1.
Conductivity (electrolytic)
–
Conductivity of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter, Conductivity measurements are used routinely in many industrial and environmental applications as a fast, inexpensive and reliable way of measuring the ionic content in a solution. For example, the measurement of product conductivity is a way to monitor. In many cases, conductivity is linked directly to the dissolved solids. High quality deionized water has a conductivity of about 5.5 μS/m, typical drinking water in the range of 5–50 mS/m, Conductivity is traditionally determined by connecting the electrolyte in a Wheatstone bridge. Dilute solutions follow Kohlrauschs Laws of concentration dependence and additivity of ionic contributions, lars Onsager gave a theoretical explanation of Kohlrauschs law by extending Debye–Hückel theory. The SI unit of conductivity is S/m and, unless otherwise qualified, often encountered in industry is the traditional unit of μS/cm. 106 μS/cm =103 mS/cm =1 S/cm, the values in μS/cm are lower than those in μS/m by a factor of 100. Sometimes encountered is mho,1 mho/m =1 S/m, historically, mhos antedate Siemens by many decades, good vacuum-tube testers, for instance, gave transconductance readings in micromhos. The commonly used standard cell has a width of 1 cm, ultra-pure water could achieve 18 megohms or more. Thus in the past, megohm-cm was used, sometimes abbreviated to megohm, sometimes, conductivity is given in microSiemens. While this is an error, it can often be assumed to be equal to the traditional μS/cm, the conversion of conductivity to the total dissolved solids depends on the chemical composition of the sample and can vary between 0.54 and 0.96. Typically, the conversion is done assuming that the solid is sodium chloride, molar conductivity has the SI unit S m2 mol−1. Older publications use the unit Ω−1 cm2 mol−1, the electrical conductivity of a solution of an electrolyte is measured by determining the resistance of the solution between two flat or cylindrical electrodes separated by a fixed distance. An alternating voltage is used in order to avoid electrolysis, the resistance is measured by a conductivity meter. Typical frequencies used are in the range 1–3 kHz, the dependence on the frequency is usually small, but may become appreciable at very high frequencies, an effect known as the Debye–Falkenhagen effect. A wide variety of instrumentation is commercially available, there are two types of cell, the classical type with flat or cylindrical electrodes and a second type based on induction. Many commercial systems offer automatic temperature correction, tables of reference conductivities are available for many common solutions
Conductivity (electrolytic)
–
Resistivity of pure water (in MΩ-cm) as a function of temperature
2.
Cation
–
An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
Cation
3.
Anion
–
An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
Anion
4.
Electric potential
–
An electric potential is the amount of work needed to move a unit positive charge from a reference point to a specific point inside the field without producing any acceleration. Typically, the point is Earth or a point at Infinity. By dividing out the charge on the particle a remainder is obtained that is a property of the field itself. This value can be calculated in either a static or an electric field at a specific time in units of joules per coulomb. The electric potential at infinity is assumed to be zero, a generalized electric scalar potential is also used in electrodynamics when time-varying electromagnetic fields are present, but this can not be so simply calculated. The electric potential and the vector potential together form a four vector. Classical mechanics explores concepts such as force, energy, potential etc, force and potential energy are directly related. A net force acting on any object will cause it to accelerate, as it rolls downhill its potential energy decreases, being translated to motion, inertial energy. It is possible to define the potential of certain force fields so that the energy of an object in that field depends only on the position of the object with respect to the field. Two such force fields are the field and an electric field. Such fields must affect objects due to the properties of the object. Objects may possess a property known as charge and an electric field exerts a force on charged objects. If the charged object has a charge the force will be in the direction of the electric field vector at that point while if the charge is negative the force will be in the opposite direction. The magnitude of the force is given by the quantity of the charge multiplied by the magnitude of the field vector. The electric potential at a point r in an electric field E is given by the line integral where C is an arbitrary path connecting the point with zero potential to r. When the curl ∇ × E is zero, the integral above does not depend on the specific path C chosen. The concept of electric potential is linked with potential energy. A test charge q has a potential energy UE given by U E = q V
Electric potential
–
Electromagnetism
Electric potential
–
The electric potential created by a charge Q is V = Q /(4πε o r). Different values of Q will make different values of electric potential V (shown in the image).
5.
Salt (chemistry)
–
In chemistry, a salt is an ionic compound that results from the neutralization reaction of an acid and a base. Salts are composed of related numbers of cations and anions so that the product is electrically neutral and these component ions can be inorganic, such as chloride, or organic, such as acetate, and can be monatomic, such as fluoride, or polyatomic, such as sulfate. There are several varieties of salts, salts that hydrolyze to produce hydroxide ions when dissolved in water are alkali salts, whilst those that hydrolyze to produce hydronium ions in water are acidic salts. Neutral salts are those salts that are neither acidic nor basic, zwitterions contain an anionic centre and a cationic centre in the same molecule, but are not considered to be salts. Examples of zwitterions include amino acids, many metabolites, peptides, usually, non-dissolved salts at standard conditions for temperature and pressure are solid, but there are exceptions. Molten salts and solutions containing dissolved salts are called electrolytes, as they are able to conduct electricity. As observed in the cytoplasm of cells, in blood, urine, plant saps and mineral waters, therefore, their salt content is given for the respective ions. Salts can appear to be clear and transparent, opaque, and even metallic, in many cases, the apparent opacity or transparency are only related to the difference in size of the individual monocrystals. Since light reflects from the boundaries, larger crystals tend to be transparent. The color of the salt is due to the electronic structure in the d-orbitals of transition elements or in the conjugated organic dye framework. Different salts can elicit all five basic tastes, e. g. salty, sweet, sour, bitter, and umami or savory. Salts of strong acids and strong bases are non-volatile and odorless and that slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts. Many ionic compounds can be dissolved in water or other similar solvents, the exact combination of ions involved makes each compound have a unique solubility in any solvent. The solubility is dependent on how well each ion interacts with the solvent, for example, all salts of sodium, potassium and ammonium are soluble in water, as are all nitrates and many sulfates – barium sulfate, calcium sulfate and lead sulfate are examples of exceptions. However, ions that bind tightly to each other and form highly stable lattices are less soluble, for example, most carbonate salts are not soluble in water, such as lead carbonate and barium carbonate. Some soluble carbonate salts are, sodium carbonate, potassium carbonate, solid salts do not conduct electricity. Moreover, solutions of salts also conduct electricity, the name of a salt starts with the name of the cation followed by the name of the anion. Salts are often referred to only by the name of the cation or by the name of the anion. g
Salt (chemistry)
–
The salt
copper(II) sulfate as the
mineral chalcanthite.
Salt (chemistry)
–
Potassium dichromate, a bright orange salt used as a pigment.
Salt (chemistry)
–
Solid lead(II) sulfate (PbSO 4)
6.
Acid
–
An acid is a molecule or ion capable of donating a hydron, or, alternatively, capable of forming a covalent bond with an electron pair. The first category of acids is the donors or Brønsted acids. In the special case of solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents, acids form aqueous solutions with a sour taste, can turn blue litmus red, and react with bases and certain metals to form salts. The word acid is derived from the Latin acidus/acēre meaning sour, an aqueous solution of an acid has a pH less than 7 and is colloquially also referred to as acid, while the strict definition refers only to the solute. A lower pH means a higher acidity, and thus a higher concentration of hydrogen ions in the solution. Chemicals or substances having the property of an acid are said to be acidic, common aqueous acids include hydrochloric acid, acetic acid, sulfuric acid, and citric acid. As these examples show, acids can be solutions or pure substances, strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid. The second category of acids are Lewis acids, which form a covalent bond with an electron pair, however, hydrogen chloride, acetic acid, and most other Brønsted-Lowry acids cannot form a covalent bond with an electron pair and are therefore not Lewis acids. Conversely, many Lewis acids are not Arrhenius or Brønsted-Lowry acids, in modern terminology, an acid is implicitly a Brønsted acid and not a Lewis acid, since chemists almost always refer to a Lewis acid explicitly as a Lewis acid. Modern definitions are concerned with the chemical reactions common to all acids. Most acids encountered in life are aqueous solutions, or can be dissolved in water, so the Arrhenius. The Brønsted-Lowry definition is the most widely used definition, unless otherwise specified, hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids, they can function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms. The Swedish chemist Svante Arrhenius attributed the properties of acidity to hydrogen ions or protons in 1884, an Arrhenius acid is a substance that, when added to water, increases the concentration of H+ ions in the water. Thus, an Arrhenius acid can also be described as a substance that increases the concentration of ions when added to water. Examples include molecular substances such as HCl and acetic acid, an Arrhenius base, on the other hand, is a substance which increases the concentration of hydroxide ions when dissolved in water. Thus, an Arrhenius acid could also be said to be one that decreases hydroxide concentration, in an acidic solution, the concentration of hydronium ions is greater than 10−7 moles per liter
Acid
–
Zinc, a typical metal, reacting with
hydrochloric acid, a typical acid
Acid
–
Svante Arrhenius
Acid
–
Hydrochloric acid (in
beaker) reacting with
ammonia fumes to produce
ammonium chloride (white smoke).
7.
DNA
–
Deoxyribonucleic acid is a molecule that carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and RNA are nucleic acids, alongside proteins, lipids and complex carbohydrates, most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. The two DNA strands are termed polynucleotides since they are composed of simpler units called nucleotides. Each nucleotide is composed of one of four nitrogen-containing nucleobases—cytosine, guanine, adenine, or thymine —a sugar called deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. The nitrogenous bases of the two polynucleotide strands are bound together, according to base pairing rules, with hydrogen bonds to make double-stranded DNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037, in comparison the total mass of the biosphere has been estimated to be as much as 4 trillion tons of carbon. The DNA backbone is resistant to cleavage, and both strands of the double-stranded structure store the same biological information and this information is replicated as and when the two strands separate. A large part of DNA is non-coding, meaning that these sections do not serve as patterns for protein sequences, the two strands of DNA run in opposite directions to each other and are thus antiparallel. Attached to each sugar is one of four types of nucleobases and it is the sequence of these four nucleobases along the backbone that encodes biological information. RNA strands are created using DNA strands as a template in a process called transcription, under the genetic code, these RNA strands are translated to specify the sequence of amino acids within proteins in a process called translation. Within eukaryotic cells DNA is organized into structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, eukaryotic organisms store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast prokaryotes store their DNA only in the cytoplasm, within the eukaryotic chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed, DNA was first isolated by Friedrich Miescher in 1869. DNA is used by researchers as a tool to explore physical laws and theories, such as the ergodic theorem. The unique material properties of DNA have made it an attractive molecule for material scientists and engineers interested in micro-, among notable advances in this field are DNA origami and DNA-based hybrid materials. DNA is a polymer made from repeating units called nucleotides
DNA
–
T7 RNA polymerase (blue) producing a mRNA (green) from a DNA template (orange).
DNA
–
The structure of the DNA
double helix. The
atoms in the structure are colour-coded by
element and the detailed structure of two base pairs are shown in the bottom right.
DNA
–
Sculpture of DNA made out of shopping carts
DNA
–
James Watson and
Francis Crick (right), co-originators of the double-helix model, with Maclyn McCarty (left).
8.
Polypeptides
–
Peptides are biologically occurring short chains of amino acid monomers linked by peptide bonds. The covalent chemical bonds are formed when the group of one amino acid reacts with the amine group of another. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a peptide bond, followed by tripeptides, tetrapeptides. A polypeptide is a long, continuous, and unbranched peptide chain, hence, peptides fall under the broad chemical classes of biological oligomers and polymers, alongside nucleic acids, oligosaccharides and polysaccharides, etc. Peptides are distinguished from proteins on the basis of size, all peptides except cyclic peptides have an N-terminal and C-terminal residue at the end of the peptide. Ribosomal peptides Ribosomal peptides are synthesized by translation of mRNA and they are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules, some organisms produce peptides as antibiotics, such as microcins. Since they are translated, the amino acid residues involved are restricted to those utilized by the ribosome, however, these peptides frequently have posttranslational modifications such as phosphorylation, hydroxylation, sulfonation, palmitoylation, glycosylation and disulfide formation. In general, they are linear, although lariat structures have been observed, more exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids in platypus venom. Nonribosomal peptides Nonribosomal peptides are assembled by enzymes that are specific to each peptide, the most common non-ribosomal peptide is glutathione, which is a component of the antioxidant defenses of most aerobic organisms. Other nonribosomal peptides are most common in organisms, plants. These complexes are often out in a similar fashion. These peptides are often cyclic and can have highly complex cyclic structures, since the system is closely related to the machinery for building fatty acids and polyketides, hybrid compounds are often found. The presence of oxazoles or thiazoles often indicates that the compound was synthesized in this fashion, Peptones See also Tryptone Peptones are derived from animal milk or meat digested by proteolysis. In addition to containing small peptides, the material includes fats, metals, salts, vitamins. Peptones are used in nutrient media for growing bacteria and fungi, Peptide fragments Peptide fragments refer to fragments of proteins that are used to identify or quantify the source protein. Peptides received prominence in molecular biology for several reasons, the first is that peptides allow the creation of peptide antibodies in animals without the need of purifying the protein of interest. This involves synthesizing antigenic peptides of sections of the protein of interest and these will then be used to make antibodies in a rabbit or mouse against the protein
Polypeptides
–
A tetrapeptide (example
Val -
Gly -
Ser -
Ala) with green marked
amino end (
L-Valine) and blue marked
carboxyl end (
L-Alanine).
9.
Polyelectrolyte
–
Polyelectrolytes are polymers whose repeating units bear an electrolyte group. These groups dissociate in aqueous solutions, making the polymers charged, polyelectrolyte properties are thus similar to both electrolytes and polymers and are sometimes called polysalts. Like salts, their solutions are electrically conductive, like polymers, their solutions are often viscous. Charged molecular chains, commonly present in soft matter systems, play a role in determining structure, stability. For instance, polypeptides, glycosaminoglycans, and DNA are polyelectrolytes, both natural and synthetic polyelectrolytes are used in a variety of industries. Acids are classified as weak or strong. Similarly, polyelectrolytes can be divided into weak and strong types, a strong polyelectrolyte is one that dissociates completely in solution for most reasonable pH values. A weak polyelectrolyte, by contrast, has a constant in the range of ~2 to ~10. Thus, weak polyelectrolytes are not fully charged in solution, and moreover their fractional charge can be modified by changing the solution pH, counter-ion concentration, the physical properties of polyelectrolyte solutions are usually strongly affected by this degree of charging. Since the polyelectrolyte dissociation releases counter-ions, this affects the solutions ionic strength. This in turn affects other properties, such as electrical conductivity, when solutions of two oppositely charged polymers are mixed, a bulk complex is usually formed. This occurs because the oppositely-charged polymers attract one another and bind together, the conformation of any polymer is affected by a number of factors, notably the polymer architecture and the solvent affinity. In the case of polyelectrolytes, charge also has an effect, if the solution contains a great deal of added salt, the charges will be screened and consequently the polyelectrolyte chain will collapse to a more conventional conformation. Polymer conformation of course affects many bulk properties, techniques such as static light scattering can be used to study polyelectrolyte conformation and conformational changes. Polyelectrolytes that bear both cationic and anionic repeat groups are called polyampholytes, the competition between the acid-base equilibria of these groups leads to additional complications in their physical behavior. These polymers usually only dissolve when there is sufficient added salt, in case of amphoteric macroporous hydrogels action of concentrated salt solution does not lead to dissolution of polyampholyte material due to covalent cross-linking of macromolecules. Polyelectrolytes have many applications, mostly related to modifying flow and stability properties of aqueous solutions, for instance, they can be used to destabilize a colloidal suspension and to initiate flocculation. They can also be used to impart a surface charge to neutral particles and they are thus often used as thickeners, emulsifiers, conditioners, clarifying agents, and even drag reducers
Polyelectrolyte
–
Chemical structures of two synthetic polyelectrolytes, as examples. To the left is
poly(sodium styrene sulfonate) (PSS), and to the right is
polyacrylic acid (PAA). Both are negatively charged polyelectrolytes when dissociated. PSS is a 'strong' polyelectrolyte (fully charged in solution), whereas PAA is 'weak' (partially charged).
10.
Functional group
–
In organic chemistry, functional groups are specific groups of atoms or bonds within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of, however, its relative reactivity can be modified by other functional groups nearby. The atoms of functional groups are linked to other and to the rest of the molecule by covalent bonds. Any subgroup of atoms of a compound also may be called a radical, and if a covalent bond is broken homolytically, Functional groups can also be charged, e. g. in carboxylate salts, which turns the molecule into a polyatomic ion or a complex ion. Complexation and solvation is also caused by interactions of functional groups. In the common rule of thumb like dissolves like, it is the shared or mutually well-interacting functional groups give rise to solubility. For example, sugar dissolves in water because both share the functional group and hydroxyls interact strongly with each other. Combining the names of groups with the names of the parent alkanes generates what is termed a systematic nomenclature for naming organic compounds. In traditional nomenclature, the first carbon atom after the carbon that attaches to the group is called the alpha carbon, the second, beta carbon. IUPAC conventions call for numeric labeling of the position, e. g. 4-aminobutanoic acid, in traditional names various qualifiers are used to label isomers, for example isopropanol is an isomer is n-propanol. The following is a list of functional groups. In the formulas, the symbols R and R usually denote an attached hydrogen, or a side chain of any length. Functional groups, called hydrocarbyl, that only carbon and hydrogen. Each one differs in type of reactivity, there are also a large number of branched or ring alkanes that have specific names, e. g. tert-butyl, bornyl, cyclohexyl, etc. Hydrocarbons may form charged structures, positively charged carbocations or negative carbanions, examples are tropylium and triphenylmethyl cations and the cyclopentadienyl anion. Haloalkanes are a class of molecule that is defined by a carbon–halogen bond and this bond can be relatively weak or quite stable. In general, with the exception of fluorinated compounds, haloalkanes readily undergo nucleophilic substitution reactions or elimination reactions, the substitution on the carbon, the acidity of an adjacent proton, the solvent conditions, etc. all can influence the outcome of the reactivity. Compounds that contain nitrogen in this category may contain C-O bonds, compounds that contain sulfur exhibit unique chemistry due to their ability to form more bonds than oxygen, their lighter analogue on the periodic table
Functional group
–
Benzyl acetate has an ester functional group (in red), an acetyl moiety (circled with dark green) and a benzyloxy moiety (circled with light orange). Other divisions can be made.
11.
Svante Arrhenius
–
Svante August Arrhenius was a Nobel-Prize winning Swedish scientist, originally a physicist, but often referred to as a chemist, and one of the founders of the science of physical chemistry. He received the Nobel Prize for Chemistry in 1903, becoming the first Swedish Nobel laureate, Arrhenius was born on 19 February 1859 at Vik, near Uppsala, Sweden, the son of Svante Gustav and Carolina Thunberg Arrhenius. His father had been a surveyor for Uppsala University, moving up to a supervisory position. At the age of three, Arrhenius taught himself to read without the encouragement of his parents, and by watching his fathers addition of numbers in his account books, in later life, Arrhenius enjoyed using masses of data to discover mathematical relationships and laws. At age eight, he entered the cathedral school, starting in the fifth grade, distinguishing himself in physics and mathematics. His work focused on the conductivities of electrolytes, in 1884, based on this work, he submitted a 150-page dissertation on electrolytic conductivity to Uppsala for the doctorate. It did not impress the professors, among whom was Cleve, and he received a fourth-class degree, later, extensions of this very work would earn him the 1903 Nobel Prize in Chemistry. Arrhenius put forth 56 theses in his 1884 dissertation, most of which would still be accepted today unchanged or with minor modifications, Arrhenius explanation was that in forming a solution, the salt disassociates into charged particles. Faradays belief had been that ions were produced in the process of electrolysis, Arrhenius proposed that, even in the absence of an electric current and he thus proposed that chemical reactions in solution were reactions between ions. They were far more impressed, and Ostwald even came to Uppsala to persuade Arrhenius to join his research team, Arrhenius declined, however, as he preferred to stay in Sweden for a while and had received an appointment at Uppsala. In an extension of his ionic theory Arrhenius proposed definitions for acids and bases and he believed that acids were substances that produce hydrogen ions in solution and that bases were substances that produce hydroxide ions in solution. The Arrhenius equation gives the basis of the relationship between the activation energy and the rate at which a reaction proceeds. In 1891 he became a lecturer at the Stockholm University College, being promoted to professor of physics in 1895, and rector in 1896. He was married twice, first to his former pupil Sofia Rudbeck, with whom he had one son Olof Arrhenius, about 1900, Arrhenius became involved in setting up the Nobel Institutes and the Nobel Prizes. He was elected a member of the Royal Swedish Academy of Sciences in 1901, for the rest of his life, he would be a member of the Nobel Committee on Physics and a de facto member of the Nobel Committee on Chemistry. He used his positions to arrange prizes for his friends and to attempt to deny them to his enemies, in 1901 Arrhenius was elected to the Swedish Academy of Sciences, against strong opposition. In 1903 he became the first Swede to be awarded the Nobel Prize in chemistry, in 1905, upon the founding of the Nobel Institute for Physical Research at Stockholm, he was appointed rector of the institute, the position where he remained until retirement in 1927. He was elected a Foreign Member of the Royal Society in 1910, in 1911 he won the first Willard Gibbs Award
Svante Arrhenius
–
Svante Arrhenius
Svante Arrhenius
–
Arrhenius' family grave in
Uppsala
Svante Arrhenius
–
Arrhenius at the first Solvay conference on chemistry in 1922 in
Brussels.
Svante Arrhenius
–
Svante Arrhenius (1909)
12.
Michael Faraday
–
Michael Faraday FRS was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic induction, diamagnetism, although Faraday received little formal education, he was one of the most influential scientists in history. It was by his research on the field around a conductor carrying a direct current that Faraday established the basis for the concept of the electromagnetic field in physics. Faraday also established that magnetism could affect rays of light and that there was a relationship between the two phenomena. He similarly discovered the principles of induction and diamagnetism. His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, Faraday ultimately became the first and foremost Fullerian Professor of Chemistry at the Royal Institution of Great Britain, a lifetime position. James Clerk Maxwell took the work of Faraday and others and summarized it in a set of equations which is accepted as the basis of all theories of electromagnetic phenomena. The SI unit of capacitance is named in his honour, the farad, albert Einstein kept a picture of Faraday on his study wall, alongside pictures of Isaac Newton and James Clerk Maxwell. Faraday was born in Newington Butts, which is now part of the London Borough of Southwark but was then a part of Surrey. His family was not well off and his father, James, was a member of the Glassite sect of Christianity. James Faraday moved his wife and two children to London during the winter of 1790 from Outhgill in Westmorland, where he had been an apprentice to the village blacksmith, Michael was born in the autumn of that year. The young Michael Faraday, who was the third of four children, at the age of 14 he became an apprentice to George Riebau, a local bookbinder and bookseller in Blandford Street. During his seven-year apprenticeship Faraday read many books, including Isaac Wattss The Improvement of the Mind, at this time he also developed an interest in science, especially in electricity. Faraday was particularly inspired by the book Conversations on Chemistry by Jane Marcet, many of the tickets for these lectures were given to Faraday by William Dance, who was one of the founders of the Royal Philharmonic Society. Faraday subsequently sent Davy a 300-page book based on notes that he had taken during these lectures, davys reply was immediate, kind, and favourable. In 1813, when Davy damaged his eyesight in an accident with nitrogen trichloride, very soon Davy entrusted Faraday with the preparation of nitrogen trichloride samples, and they both were injured in an explosion of this very sensitive substance. In the class-based English society of the time, Faraday was not considered a gentleman, Faraday was forced to fill the role of valet as well as assistant throughout the trip. Davys wife, Jane Apreece, refused to treat Faraday as an equal, the trip did, however, give him access to the scientific elite of Europe and exposed him to a host of stimulating ideas
Michael Faraday
–
Michael Faraday, 1842
Michael Faraday
–
External video
Michael Faraday
–
Portrait of Faraday in his late thirties
Michael Faraday
–
Michael Faraday, ca. 1861
13.
Electrolysis
–
In chemistry and manufacturing, electrolysis is a technique that uses a direct electric current to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential, nevertheless, electrolysis, as a tool to study chemical reactions and obtain pure elements, precedes the coinage of the term and formal description by Faraday. 1785 – Martinus van Marums electrostatic generator was used to reduce tin, zinc,1800 – William Nicholson and Anthony Carlisle, decomposed water into hydrogen and oxygen. 1808 – Potassium, sodium, barium, calcium and magnesium were discovered by Sir Humphry Davy using electrolysis,1821 – Lithium was discovered by the English chemist William Thomas Brande, who obtained it by electrolysis of lithium oxide. 1833 – Michael Faraday develops his two laws of electrolysis, and provides an explanation of his laws. 1875 – Paul Émile Lecoq de Boisbaudran discovered gallium using electrolysis,1886 – Fluorine was discovered by Henri Moissan using electrolysis. The main components required to achieve electrolysis are, An electrolyte, a substance, frequently an ion-conducting polymer that contains free ions, if the ions are not mobile, as in a solid salt then electrolysis cannot occur. A direct current electrical supply, provides the necessary to create or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit, two electrodes, electrical conductors that provide the physical interface between the electrolyte and the electrical circuit that provides the energy. Electrodes of metal, graphite and semiconductor material are widely used, choice of suitable electrode depends on chemical reactivity between the electrode and electrolyte and manufacturing cost. The key process of electrolysis is the interchange of atoms and ions by the removal or addition of electrons from the external circuit, the desired products of electrolysis are often in a different physical state from the electrolyte and can be removed by some physical processes. For example, in the electrolysis of brine to produce hydrogen and chlorine and these gaseous products bubble from the electrolyte and are collected. Each electrode attracts ions that are of the opposite charge, positively charged ions move towards the electron-providing cathode. Negatively charged ions move towards the electron-extracting anode, in this process electrons are either absorbed or released. Neutral atoms gain or lose electrons and become charged ions that pass into the electrolyte. The formation of uncharged atoms from ions is called discharging, when an ion gains or loses enough electrons to become uncharged atoms, the newly formed atoms separate from the electrolyte. Positive metal ions like Cu++ deposit onto the cathode in a layer, the terms for this are electroplating, electrowinning, and electrorefining
Electrolysis
–
Illustration of an electrolysis apparatus used in a school laboratory.
14.
Thermodynamic
–
Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. The behavior of these quantities is governed by the four laws of thermodynamics, the laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a variety of topics in science and engineering, especially physical chemistry, chemical engineering. The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds, Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged in the following decades, statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a mathematical approach to the field in his axiomatic formulation of thermodynamics. A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis, the first law specifies that energy can be exchanged between physical systems as heat and work. In thermodynamics, interactions between large ensembles of objects are studied and categorized, central to this are the concepts of the thermodynamic system and its surroundings. A system is composed of particles, whose average motions define its properties, properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. With these tools, thermodynamics can be used to describe how systems respond to changes in their environment and this can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, and even black holes. This article is focused mainly on classical thermodynamics which primarily studies systems in thermodynamic equilibrium, non-equilibrium thermodynamics is often treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field. Guericke was driven to make a vacuum in order to disprove Aristotles long-held supposition that nature abhors a vacuum. Shortly after Guericke, the English physicist and chemist Robert Boyle had learned of Guerickes designs and, in 1656, in coordination with English scientist Robert Hooke, using this pump, Boyle and Hooke noticed a correlation between pressure, temperature, and volume. In time, Boyles Law was formulated, which states that pressure, later designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and he did not, however, follow through with his design. Nevertheless, in 1697, based on Papins designs, engineer Thomas Savery built the first engine, although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time. Black and Watt performed experiments together, but it was Watt who conceived the idea of the condenser which resulted in a large increase in steam engine efficiency. Drawing on all the work led Sadi Carnot, the father of thermodynamics, to publish Reflections on the Motive Power of Fire
Thermodynamic
–
Annotated color version of the original 1824
Carnot heat engine showing the hot body (boiler), working body (system, steam), and cold body (water), the letters labeled according to the stopping points in
Carnot cycle
15.
Solvation
–
Solvation, also sometimes called dissolution, is the attraction and association of molecules of a solvent with molecules or ions of a solute. When a solute is soluble in a solvent, the solute’s molecules or ions will spread out. A molecule or ion of solute surrounded by solvent is known as a solvation complex, solvation is the process of reorganizing solvent and solute molecules into solvation complexes until the solute is distributed evenly within the solvent. Solvation depends on such as hydrogen bonding and van der Waals forces. Insoluble solutes prefer to maintain interactions among solute molecules rather than break apart, solvation of a solute by water is called hydration. By an IUPAC definition, solvation is an interaction of a solute with the solvent, in the solvated state, an ion in a solution is surrounded or complexed by solvent molecules. Solvated species can be described by number and the complex stability constants. The concept of the interaction can also be applied to an insoluble material, for example. Solvation is, in concept, distinct from solubility, solvation or dissolution is a kinetic process and is quantified by its rate. Solubility quantifies the dynamic equilibrium state achieved when the rate of dissolution equals the rate of precipitation, the consideration of the units makes the distinction clearer. The typical unit for dissolution rate is mol/s, the units for solubility express a concentration, mass per volume, molarity, etc. Solvation involves different types of interactions, hydrogen bonding, ion-dipole interactions. Which of these forces are at play depends on the structure and properties of the solvent. The similarity or complementary character of these properties between solvent and solute determines how well a solute can be solvated by a particular solvent, Solvent polarity is the most important factor in determining how well it solvates a particular solute. Polar solvents have molecular dipoles, meaning part of the solvent molecule has more electron density than another part of the molecule. The part with more electron density will experience a negative charge while the part with less electron density will experience a partial positive charge. Polar solvent molecules can solvate polar solutes and ions because they can orient the appropriate partially charged portion of the molecule towards the solute through electrostatic attraction and this stabilizes the system and creates a solvation shell around each particle of solute. Water is the most common and well-studied polar solvent, but others exist, such as ethanol, methanol, acetone, acetonitrile, polar solvents are often found to have a high dielectric constant, although other solvent scales are also used to classify solvent polarity
Solvation
–
A sodium ion solvated by water molecules. It has to be assumed that delta on hydrogen is 1/2 of delta on oxygen for this diagram to be correct. [
clarification needed]
16.
Hydronium
–
In chemistry, hydronium is the common name for the aqueous cation H 3O+, the type of oxonium ion produced by protonation of water. It is the ion present when an Arrhenius acid is dissolved in water. It is the amount of hydronium ions relative to hydroxide ions that determines a solutions pH, at 25 °C, water has a pH of 7. A pH value less than 7 indicates an acidic solution, according to IUPAC nomenclature of organic chemistry, the hydronium ion should be referred to as oxonium. Hydroxonium may also be used unambiguously to identify it, a draft IUPAC proposal also recommends the use of oxonium and oxidanium in organic and inorganic chemistry contexts, respectively. An oxonium ion is any ion with a trivalent oxygen cation, for example, a protonated hydroxyl group is an oxonium ion, but not a hydronium ion. Since O+ and N have the number of electrons, H 3O+ is isoelectronic with ammonia. As shown in the images above, H 3O+ has a pyramidal molecular geometry with the oxygen atom at its apex. The H–O–H bond angle is approximately 113°, and the center of mass is close to the oxygen atom. Because the base of the pyramid is made up of three hydrogen atoms, the H 3O+ molecules symmetric top configuration is such that it belongs to the C3v point group. Because of this symmetry and the fact that it has a dipole moment, the transition dipole lies along the c-axis and, because the negative charge is localized near the oxygen atom, the dipole moment points to the apex, perpendicular to the base plane. Hydronium is the cation that forms from water in the presence of hydrogen ions and these hydrons do not exist in a free state, they are extremely reactive and are solvated by water. An acidic solute is generally the source of these hydrons, however and this special case of water reacting with water to produce hydronium ions is commonly known as the self-ionization of water. The resulting hydronium ions are few and short-lived, PH is a measure of the relative activity of hydronium and hydroxide ions in aqueous solutions. In acidic solutions, hydronium is the active, its excess proton being readily available for reaction with basic species. The hydronium ion is very acidic, at 25 °C, its pKa is 0 and it is the most acidic species that can exist in water, any stronger acid will ionize and protonate a water molecule to form hydronium. PH was originally conceived to be a measure of the ion concentration of aqueous solution. We now know that all such free protons quickly react with water to form hydronium
Hydronium
–
Zundel cation
17.
Carbonate
–
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, a polyatomic ion with the formula of CO2−3. The name may mean an ester of carbonic acid, an organic compound containing the carbonate group C2. In geology and mineralogy, the term carbonate can refer both to carbonate minerals and carbonate rock, and both are dominated by the ion, CO2−3. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock, sodium carbonate and potassium carbonate have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass. Carbonates are widely used in industry, e. g. in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, the carbonate ion is the simplest oxocarbon anion. It consists of one carbon atom surrounded by three oxygen atoms, in a planar arrangement, with D3h molecular symmetry. It has a mass of 60.01 g/mol and carries a total formal charge of −2. It is the base of the hydrogen carbonate ion, HCO−3. The Lewis structure of the ion has two single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen. This structure is incompatible with the symmetry of the ion. This process is called calcination, after calx, the Latin name of quicklime or calcium oxide, CaO, exceptions include lithium, sodium, potassium and ammonium carbonates, as well as many uranium carbonates. In aqueous solution, carbonate, bicarbonate, carbon dioxide, in strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide, CO2, is the main form, thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid. Carbonated water is formed by dissolving CO2 in water under pressure, in living systems an enzyme, carbonic anhydrase, speeds the interconversion of CO2 and carbonic acid. Although the carbonate salts of most metals are insoluble in water, in solution this equilibrium between carbonate, bicarbonate, carbon dioxide and carbonic acid changes consonant to changing temperature and pressure conditions. In the case of ions with insoluble carbonates, e. g. CaCO3. This is an explanation for the buildup of scale inside pipes caused by hard water, in organic chemistry a carbonate can also refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of which is double bonded. These compounds are known as organocarbonates or carbonate esters, and have the general formula ROCOOR′
Carbonate
–
Carbonate
18.
Carbonic Acid
–
Not to be confused with Carbolic acid, an antiquated name for phenol. Carbonic acid is a compound with the chemical formula H2CO3. It is also a name given to solutions of carbon dioxide in water. In physiology, carbonic acid is described as acid or respiratory acid. It plays an important role in the buffer system to maintain acid–base homeostasis. Carbonic acid, which is an acid, forms two kinds of salts, the carbonates and the bicarbonates. In geology, carbonic acid causes limestone to dissolve producing calcium bicarbonate which leads to many features such as stalactites and stalagmites. It was long believed that carbonic acid could not exist as a pure compound, however, in 1991 it was reported that NASA scientists had succeeded in making solid H2CO3 samples. 7×10−3 in pure water and ≈1. 2×10−3 in seawater. Hence, the majority of the dioxide is not converted into carbonic acid. In the absence of a catalyst, the equilibrium is reached quite slowly, the rate constants are 0.039 s−1 for the forward reaction and 23 s−1 for the reverse reaction. The addition of two molecules of water to CO2 would give orthocarbonic acid, C4, which only in minute amounts in aqueous solution. Addition of base to an excess of acid gives bicarbonate. With excess base, carbonic acid reacts to give carbonate salts, bicarbonate is an intermediate in the transport of CO2 out of the body via respiratory gas exchange. This catalysed reaction is reversed in the lungs, where it converts the bicarbonate back into CO2 and this equilibration plays an important role as a buffer in mammalian blood. A2016 theoretical report suggests that carbonic acid may play a role in protonating various nitrogen bases in blood serum. The oceans of the world have absorbed almost half of the CO2 emitted by humans from the burning of fossil fuels and it has been theorized that the extra dissolved carbon dioxide has caused the oceans average surface pH to shift by about −0.1 unit from pre-industrial levels. This theory is known as acidification, even though the ocean remains basic. Carbonic acid is a polyprotic acid — specifically it is diprotic meaning it has two protons which may dissociate from the parent molecule
Carbonic Acid
19.
Physiology
–
Physiology is the scientific study of normal mechanisms, and their interactions, which operate within a living system. A sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system. Given the size of the field, it is divided into, among others, animal physiology, plant physiology, cellular physiology, microbial physiology, bacterial physiology, and viral physiology. The Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences. In medicine, a state is one occurring from normal body function, rather than pathologically. Physiological studies date back to the ancient civilizations of India and Egypt alongside anatomical studies, the study of human physiology as a medical field dates back to at least 420 BC to the time of Hippocrates, also known as the father of medicine. Hippocrates incorporated his belief called the theory of humours, which consisted of four basic substance, earth, water, air. Each substance is known for having a corresponding humour, black bile, phlegm, blood and yellow bile, Hippocrates also noted some emotional connections to the four humours, which Claudis Galenus would later expand on. The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the theory of disease. Claudius Galenus, known as Galen of Pergamum, was the first to use experiments to probe the functions of the body, unlike Hippocrates though, Galen argued that humoral imbalances can be located in specific organs, including the entire body. His modification of this theory better equipped doctors to more precise diagnoses. Galen was also the founder of experimental physiology, and for the next 1,400 years, Galenic physiology was a powerful and influential tool in medicine. Jean Fernel, a French physician, introduced the term physiology, inspired in the work of Adam Smith, Milne-Edwards wrote that the body of all living beings, whether animal or plant, resembles a factory. Where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual, in more differentiated organisms, the functional labor could be apportioned between different instruments or systems. In 1858, Joseph Lister studied the cause of blood coagulation and inflammation that resulted after previous injuries and he later discovered and implemented antiseptics in the operating room, and as a result decreases death rate from surgery by a substantial amount. The Physiological Society was founded in London in 1876 as a dining club, the American Physiological Society is a nonprofit organization that was founded in 1887. The Society is, devoted to fostering education, scientific research, in 1891, Ivan Pavlov performed research on conditional reflexes that involved dogs saliva production in response to a plethora of sounds and visual stimuli
Physiology
–
Oil painting depicting Claude Bernard, the father of modern physiology, with his pupils
Physiology
–
Animals
20.
Sodium
–
Sodium is a chemical element with symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal, Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged atom—the Na+ cation. Its only stable isotope is 23Na, the free metal does not occur in nature, but must be prepared from compounds. Sodium is the sixth most abundant element in the Earths crust, Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful compounds, sodium hydroxide is used in soap manufacture, and sodium chloride is a de-icing agent. Sodium is an element for all animals and some plants. Sodium ions are the major cation in the fluid and as such are the major contributor to the ECF osmotic pressure. Loss of water from the ECF compartment increases the sodium concentration, isotonic loss of water and sodium from the ECF compartment decreases the size of that compartment in a condition called ECF hypovolemia. In nerve cells, the charge across the cell membrane enables transmission of the nerve impulse—an action potential—when the charge is dissipated. The melting and boiling points of sodium are lower than those of lithium but higher than those of the alkali metals potassium, rubidium. All of these high-pressure allotropes are insulators and electrides.3 nm, spin-orbit interactions involving the electron in the 3p orbital split the D line into two, at 589.0 and 589.6 nm, hyperfine structures involving both orbitals cause many more lines. Twenty isotopes of sodium are known, but only 23Na is stable, 23Na is created in the carbon-burning process in stars by fusing two carbon atoms together, this requires temperatures above 600 megakelvins and a star of at least three solar masses. Two nuclear isomers have been discovered, the one being 24mNa with a half-life of around 20.2 milliseconds. Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon. This process requires so little energy that sodium is oxidized by giving up its 11th electron. In contrast, the ionization energy is very high, because the 10th electron is closer to the nucleus than the 11th electron. As a result, sodium usually forms ionic compounds involving the Na+ cation, the most common oxidation state for sodium is +1. It is generally less reactive than potassium and more reactive than lithium, Sodium metal is highly reducing, with the reduction of sodium ions requiring −2.71 volts, though potassium and lithium have even more negative potentials
Sodium
–
Sodium, 11 Na
Sodium
–
Spectral lines of sodium
Sodium
–
Emission spectrum for sodium, showing the
D line.
Sodium
–
A positive
flame test for sodium has a bright yellow color.
21.
Potassium
–
Potassium is a chemical element with symbol K and atomic number 19. It was first isolated from potash, the ashes of plants, in the periodic table, potassium is one of the alkali metals. Potassium in nature only in ionic salts. It is found dissolved in sea water, and is part of many minerals, naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. Traces of 40K are found in all potassium, and it is the most common radioisotope in the human body, Potassium is chemically very similar to sodium, the previous element in Group 1 of the periodic table. They have a similar energy, which allows for each atom to give up its sole outer electron. That they are different elements combine with the same anions to make similar salts was suspected in 1702. Most industrial applications of potassium exploit the high solubility in water of potassium compounds, heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production. Potassium ions are necessary for the function of all living cells, fresh fruits and vegetables are good dietary sources of potassium. Potassium is the second least dense metal after lithium and it is a soft solid with a low melting point, and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air, in a flame test, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers. Neutral potassium atoms have 19 electrons, one more than the stable configuration of the noble gas argon. This process requires so little energy that potassium is readily oxidized by atmospheric oxygen, in contrast, the second ionization energy is very high, because removal of two electrons breaks the stable noble gas electronic configuration. Potassium therefore does not readily form compounds with the state of +2 or higher. Potassium is an active metal that reacts violently with oxygen in water. With oxygen it forms potassium peroxide, and with water potassium forms potassium hydroxide, the reaction of potassium with water is dangerous because of its violent exothermic character and the production of hydrogen gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium and this reaction requires only traces of water, because of this, potassium and the liquid sodium-potassium — NaK — are potent desiccants that can be used to dry solvents prior to distillation. Because of the sensitivity of potassium to water and air, reactions with other elements are only in an inert atmosphere such as argon gas using air-free techniques
Potassium
–
Potassium pearls under paraffin oil. The large pearl measures 0.5 cm.
Potassium
–
Spectral lines of potassium
Potassium
–
Potassium in
feldspar
Potassium
–
Humphry Davy
22.
Calcium
–
Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft grayish-yellow alkaline earth metal, fifth-most-abundant element by mass in the Earths crust, the ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate. Free calcium metal is too reactive to occur in nature, Calcium is produced in supernova nucleosynthesis. Calcium is a trace element in living organisms. It is the most abundant metal by mass in animals, and it is an important constituent of bone, teeth. In cell biology, the movement of the calcium ion into, Calcium carbonate and calcium citrate are often taken as dietary supplements. Calcium is on the World Health Organizations List of Essential Medicines, Calcium has a wide variety of applications, almost all of which are associated with calcium compounds and salts. Calcium metal is used as a deoxidizer, desulfurizer, and decarbonizer for production of ferrous and nonferrous alloys. In steelmaking and production of iron, Ca reacts with oxygen, Calcium carbonate is used in manufacturing cement and mortar, lime, limestone and aids in production in the glass industry. It also has chemical and optical uses as mineral specimens in toothpastes, Calcium hydroxide solution is used to detect the presence of carbon dioxide in a gas sample bubbled through a solution. The solution turns cloudy where CO2 is present, Calcium arsenate is used in insecticides. Calcium carbide is used to make acetylene gas and various plastics, Calcium chloride is used in ice removal and dust control on dirt roads, as a conditioner for concrete, as an additive in canned tomatoes, and to provide body for automobile tires. Calcium citrate is used as a food preservative, Calcium cyclamate is used as a sweetening agent in several countries. In the United States, it has been outlawed as a suspected carcinogen, Calcium gluconate is used as a food additive and in vitamin pills. Calcium hypochlorite is used as a swimming pool disinfectant, as an agent, as an ingredient in deodorant. Calcium permanganate is used in rocket propellant, textile production, as a water sterilizing agent. Calcium phosphate is used as a supplement for animal feed, fertilizer, in production for dough and yeast products, in the manufacture of glass. Calcium phosphide is used in fireworks, rodenticide, torpedoes, Calcium sulfate is used as common blackboard chalk, as well as, in its hemihydrate form, Plaster of Paris
Calcium
–
Calcium, 20 Ca
Calcium
–
Travertine terraces
Pamukkale, Turkey
Calcium
–
'Ain Ghazal figure
Calcium
–
500 milligram calcium supplements made from
calcium carbonate
23.
Magnesium
–
Magnesium is a chemical element with symbol Mg and atomic number 12. Magnesium is the ninth most abundant element in the universe and it is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earths crust and the fourth most common element in the Earth, making up 13% of the planets mass and it is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium occurs naturally only in combination with elements, where it invariably has a +2 oxidation state. The free element can be produced artificially, and is highly reactive, the free metal burns with a characteristic brilliant-white light. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine, Magnesium is less dense than aluminium, and the alloy is prized for its combination of lightness and strength. Magnesium is the eleventh most abundant element by mass in the body and is essential to all cells. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids, elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium has the lowest melting and the lowest boiling point 1,363 K of all the alkaline earth metals, Magnesium reacts with water at room temperature, though it reacts much more slowly than calcium, a similar group 2 metal. When submerged in water, hydrogen bubbles form slowly on the surface of the metal—though, if powdered, the reaction occurs faster with higher temperatures. Magnesiums reversible reaction with water can be harnessed to store energy, Magnesium also reacts exothermically with most acids such as hydrochloric acid, producing the metal chloride and hydrogen gas, similar to the HCl reaction with aluminium, zinc, and many other metals. Magnesium is highly flammable, especially when powdered or shaved into thin strips, flame temperatures of magnesium and magnesium alloys can reach 3,100 °C, although flame height above the burning metal is usually less than 300 mm. Once ignited, such fires are difficult to extinguish, with combustion continuing in nitrogen, carbon dioxide, Magnesium may also be used as an igniter for thermite, a mixture of aluminium and iron oxide powder that ignites only at a very high temperature. When burning in air, magnesium produces a light that includes strong ultraviolet wavelengths. Magnesium powder was used for illumination in the early days of photography. Later, magnesium filament was used in electrically ignited single-use photography flashbulbs, Magnesium powder is used in fireworks and marine flares where a brilliant white light is required
Magnesium
–
Magnesium, 12 Mg
Magnesium
–
Spectral lines of magnesium
Magnesium
–
Magnesium sheets and ingots
Magnesium
–
An unusual application of magnesium as an
illumination source while
wakeskating in 1931
24.
Chloride
–
The chloride ion /ˈklɔəraɪd/ is the anion Cl−. It is formed when the element chlorine gains an electron or when a compound such as chloride is dissolved in water or other polar solvents. Chloride salts such as sodium chloride are often soluble in water. It is an essential electrolyte located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses and regulating fluid in, less frequently, the word chloride may also form part of the common name of chemical compounds in which one or more chlorine atoms are covalently bonded. For example, methyl chloride, with the standard name chloromethane is a compound with a covalent C−Cl bond in which the chlorine is not an anion. A chloride ion is much larger than an atom,167 and 99 pm. The ion is colorless and diamagnetic, in aqueous solution, it is highly soluble in most cases, however, some chloride salts, such as silver chloride, lead chloride, and mercury chloride are slightly soluble in water. In aqueous solution, chloride is bound by the end of the water molecules. Some chloride-containing minerals include the chlorides of sodium, potassium, and magnesium, called serum chloride, the concentration of chloride in the blood is regulated by the kidneys. A chloride ion is a component of some proteins, e. g. it is present in the amylase enzyme. The chlor-alkali industry is a consumer of the worlds energy budget. This process converts sodium chloride into chlorine and sodium hydroxide, which are used to make many other materials and chemicals, in the petroleum industry, the chlorides are a closely monitored constituent of the mud system. An increase of the chlorides in the mud system may be an indication of drilling into a high-pressure saltwater formation and its increase can also indicate the poor quality of a target sand. Chloride is also a useful and reliable chemical indicator of river / groundwater fecal contamination, as chloride is a non-reactive solute, many water regulating companies around the world utilize chloride to check the contamination levels of the rivers and potable water sources. Chloride salts such as sodium chloride are used to preserve food, chloride is an essential electrolyte, trafficking in and out of cells through chloride channels and playing a key role in maintaining cell homeostasis and transmitting action potentials in neurons. Characteristic concentrations of chloride in model organisms are, in both E. coli and budding yeast are 10-200mM, in mammalian cell 5-100mM and in blood plasma 100mM, chloride can be oxidized but not reduced. The first oxidation, as employed in the process, is conversion to chlorine gas. Chlorine can be oxidized to other oxides and oxyanions including hypochlorite, chlorine dioxide, chlorate
Chloride
–
Crystals of sodium chloride, which, like most chloride salts is colorless and water-soluble.
25.
Hydrogen carbonate
–
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid. It is an anion with the chemical formula HCO−3. Bicarbonate serves a crucial role in the physiological pH buffering system. The term bicarbonate was coined in 1814 by the English chemist William Hyde Wollaston, the name lives on as a trivial name. It is isoelectronic with nitric acid HNO3, a bicarbonate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. Many bicarbonates are soluble in water at temperature and pressure, in particular, sodium bicarbonate contributes to total dissolved solids. Bicarbonate is alkaline, and a component of the pH buffering system of the human body. 70–75% of CO2 in the body is converted into carbonic acid and this is especially important for protecting tissues of the central nervous system, where pH changes too far outside of the normal range in either direction could prove disastrous. Bicarbonate also acts to regulate pH in the small intestine and it is released from the pancreas in response to the hormone secretin to neutralize the acidic chyme entering the duodenum from the stomach. In freshwater ecology, strong photosynthetic activity by freshwater plants in daylight releases gaseous oxygen into the water and these shift the pH upward until in certain circumstances the degree of alkalinity can become toxic to some organisms or can make other chemical constituents such as ammonia toxic. In darkness, when no photosynthesis occurs, respiration processes release carbon dioxide, the most common salt of the bicarbonate ion is sodium bicarbonate, NaHCO3, which is commonly known as baking soda. When heated or exposed to a such as acetic acid. This is used as an agent in baking. The flow of ions from rocks weathered by the carbonic acid in rainwater is an important part of the carbon cycle. Bicarbonate also serves much in the digestive system and it raises the internal pH of the stomach, after highly acidic digestive juices have finished in their digestion of food. Ammonium bicarbonate is used in digestive biscuit manufacture, in diagnostic medicine, the blood value of bicarbonate is one of several indicators of the state of acid–base physiology in the body. It is measured, along with carbon dioxide, chloride, potassium, the parameter standard bicarbonate concentration is the bicarbonate concentration in the blood at a PaCO2 of 40 mmHg, full oxygen saturation and 36 °C
Hydrogen carbonate
–
Bicarbonate
26.
Osmotic
–
It may also be used to describe a physical process in which any solvent moves across a semipermeable membrane separating two solutions of different concentrations. Osmosis can be made to do work, osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a property, meaning that the osmotic pressure depends on the molar concentration of the solute. Osmosis is a process in biological systems, as biological membranes are semipermeable. Permeability depends on solubility, charge, or chemistry, as well as solute size, water molecules travel through the plasma membrane, tonoplast membrane or protoplast by diffusing across the phospholipid bilayer via aquaporins. Osmosis provides the means by which water is transported into. The turgor pressure of a cell is maintained by osmosis across the cell membrane between the cell interior and its relatively hypotonic environment. Jean-Antoine Nollet first documented observation of osmosis in 1748, the word osmosis descends from the words endosmose and exosmose, which were coined by French physician René Joachim Henri Dutrochet from the Greek words ἔνδον, ἔξω, and ὠσμός. Osmosis is the movement of a solvent across a membrane toward a higher concentration of solute. In biological systems, the solvent is water, but osmosis can occur in other liquids, supercritical liquids. When a cell is submerged in water, the water pass through the cell membrane from an area of low solute concentration to high solute concentration. For example, if the cell is submerged in saltwater, water molecules out of the cell. If a cell is submerged in freshwater, water molecules move into the cell, when the membrane has a volume of pure water on both sides, water molecules pass in and out in each direction at exactly the same rate. There is no net flow of water through the membrane, the mechanism responsible for driving osmosis has commonly been represented in biology and chemistry texts as either the dilution of water by solute or by a solutes attraction to water. Both of these notions have been conclusively refuted, the diffusion model of osmosis is rendered untenable by the fact that osmosis can drive water across a membrane toward a higher concentration of water. The bound water model is refuted by the fact that osmosis is independent of the size of the solute molecules—a colligative property—or how hydrophilic they are, one fact to take note of is that heat from the surroundings is able to be converted into mechanical energy. Osmotic pressure is the cause of support in many plants. The osmotic entry of water raises the pressure exerted against the cell wall, until it equals the osmotic pressure
Osmotic
–
The process of osmosis over a semi-permeable membrane, the blue dots represent particles driving the osmotic gradient
27.
Rehydration
–
The management of dehydration typically involves the use of oral rehydration solution. Standard home solutions such as salted rice water, salted yogurt drinks, vegetable, clean plain water can also be one of several fluids given. There are commercial solutions such as Pedialyte, and relief agencies such as UNICEF widely distribute packets of salts, the World Health Organization describes a homemade ORS with one liter water with one teaspoon salt and six teaspoons sugar added. The WHO, however, does not generally recommend homemade solutions as how to make them is easily forgotten. Rehydration Project recommends adding the amount of sugar but only one-half a teaspoon of salt. Both agree that drinks with too much sugar or salt can make dehydration worse, in what the World Health Organization terms some dehydration, the child or adult is restless and irritable, is thirsty, and will drink eagerly. WHO recommends that if there is vomiting, don’t stop, but do pause for 5–10 minutes, with the older WHO solution, also give some clean water during rehydration. With the newer reduced-osmolarity, more dilute solution, this is not necessary, begin to offer food after the initial four-hour rehydration period with children and adults. With infants, continue to breastfeed even during rehydration as long as the infant will breastfeed, begin zinc supplementation after initial four-hour rehydration to reduce severity and duration of episode. If available, zinc supplementation should be continued for 10 to 14 days, during the initial period of rehydration, the patient should be re-assessed at least every four hours. The family should be provided with at least two days worth of ORS packets, in severe dehydration, the person may be lethargic or unconscious, drinks poorly, or may not be able to drink. Malnourished patients should receive a modified ORS which has less sodium, more potassium, for patients not malnourished, rehydration should be performed relatively rapidly by means of intravenous solution. Patients who can drink, even poorly, should be given Oral Rehydration Solution by mouth until the IV drip is running. In addition, all patients should start to receive some ORS when they are able to drink without difficulty, ORS provides additional base and potassium which may not be adequately supplied by IV fluid. Ideally, patients should be reassessed every fifteen to thirty minutes until a radial pulse is present. Hopefully, patients will graduate to the medium dehydration or some dehydration category, inadequate replacement of potassium losses during diarrhea can lead to potassium depletion and hypokalaemia especially in children with malnutrition. This can potentially cause muscle weakness, impaired kidney function, hypokalaemia is worsened when base is given to treat acidosis without simultaneously providing potassium, as happens in standard IVs including Ringers Lactate Solution. ORS can help correct potassium deficit, as can giving foods rich in potassium during diarrhea, as in above sections, for all patients, supplemental zinc can help to reduce the severity and duration of diarrhea
Rehydration
28.
Nerve
–
A nerve is an enclosed, cable-like bundle of axons in the peripheral nervous system. A nerve provides a pathway for the electrochemical nerve impulses that are transmitted along each of the axons to peripheral organs. In the central system, the analogous structures are known as tracts. Each nerve is a structure containing bundles of axons. Within a nerve, each axon is surrounded by a layer of tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of tissue called the perineurium. Finally, the nerve is wrapped in a layer of connective tissue called the epineurium. Efferent nerves conduct signals from the nervous system along motor neurons to their target muscles. Mixed nerves contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle and they are given letter-number designations according to the vertebra through which they connect to the spinal column. Cranial nerves innervate parts of the head, and connect directly to the brain and they are typically assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included. In addition, cranial nerves have descriptive names, each nerve is covered externally by a dense sheath of connective tissue, the epineurium. Underlying this is a layer of cells, the perineurium. Perineurial septae extend into the nerve and subdivide it into several bundles of fibres, surrounding each such fibre is the endoneurium. This forms a tube from the surface of the spinal cord to the level where the axon synapses with its muscle fibres. The endoneurium consists of a sleeve of material called the glycocalyx. Nerves are bundled along with vessels, since the neurons of a nerve have fairly high energy requirements. Within the endoneurium, the nerve fibres are surrounded by a low protein liquid called endoneurial fluid. This acts in a way to the cerebrospinal fluid in the central nervous system
Nerve
–
Cross-section of a nerve
Nerve
–
Micrograph demonstrating
perineural invasion of
prostate cancer.
H&E stain.
29.
Extracellular fluid
–
Extracellular fluid or extracellular fluid volume usually denotes all body fluid outside the cells. The remainder is called intracellular fluid, the ECF and ICF are the two major fluid compartments, which together account for total body water. In some animals, including mammals, the ECF can be divided into two major subcompartments, interstitial fluid and blood plasma, which make up at least 97%, the extracellular fluid also includes the transcellular fluid, which comprises about 2. 5%. One way of viewing the ECF is that it has two components, plasma and lymph as a system, and interstitial fluid for solute exchange. The interstitial portion of the extracellular fluid constitutes the milieu intérieur or internal environment which bathes the all of the bodys cells, the ECF composition is therefore crucial for their normal functions. The osmolality and glucose concentrations are similarly rigidly regulated, each within a narrow range of values, as are the partial pressures of oxygen. The volume of ECF is typically 15 L, of which 12 L is interstitial fluid and 3 L is plasma, interstitial fluid makes up 16% of human body weight, and blood plasma, 4%. The function of the fluid is firstly to provide the watery environment in which the cells of the body live. The bodys cells extract everything they need for their energy and structural metabolism from the ECF, there is a significant difference between the concentrations of sodium and potassium ions inside and outside the cell. The concentration of ions is considerably higher in the extracellular fluid than in the intracellular fluid. The converse is true of the ion concentrations inside and outside the cell. These differences cause the cell membranes of all the cells in the body to be electrically charged, with the positive charge on the outside of the cells. The electrical potential difference between the two is about 70 mV in a resting cell. This potential difference is created by ionic pumps in the membranes of cells, in several cell types special ion channels in the cell membrane can be temporarily opened under specific circumstances for a few microseconds at a time. This allows a brief inflow of sodium ions into the cell and this causes the cell membrane to temporarily depolarize forming the basis of ‘’nerve impulses”. These action potentials are important means of communication along nerve fibers as well as muscle fibres. These events can occur if the concentrations of sodium and potassium ions in the ECF are at their correct values. The sodium ions in the ECF also play an important role in the movement of water from one compartment to the other
Extracellular fluid
–
Extracellular fluid content in humans
30.
Interstitial fluid
–
Interstitial fluid or tissue fluid is a solution that bathes and surrounds the tissue cells of multicellular animals. It is the component of the extracellular fluid, which also includes plasma. The interstitial fluid is found in the interstices - the spaces between cells, on average, a person has about 10 litres of interstitial fluid, providing the cells of the body with nutrients and a means of waste removal. Plasma and interstitial fluid are very similar and this similarity exists because water, ions, and small solutes are continuously exchanged between plasma and interstitial fluids across the walls of capillaries. Plasma, the component in blood, communicates freely with interstitial fluid through pores. Hydrostatic pressure is generated by the force of the heart. It pushes water out of the capillaries, the water potential is created due to the inability of certain blood proteins to pass through the walls of capillaries. The build-up of these proteins within the capillaries induces osmosis, the water passes from a high concentration outside of the vessels to a low concentration inside of the vessels, in an attempt to reach an equilibrium. The osmotic pressure drives water back into the vessels, because the blood in the capillaries is constantly flowing, equilibrium is never reached. The balance between the two forces differs at different points on the capillaries, at the arterial end of a vessel, the hydrostatic pressure is greater than the osmotic pressure, so the net movement favors water and other solutes being passed into the tissue fluid. At the venous end, the pressure is greater, so the net movement favors substances being passed back into the capillary. This difference is created by the direction of the flow of blood, to prevent a build-up of tissue fluid surrounding the cells in the tissue, complementing the venous system is the lymphatic system, which plays a part in the transport of tissue fluid. Tissue fluid can pass into the lymph vessels, and eventually ends up rejoining the blood. Sometimes the removal of fluid does not function correctly. This can cause swelling, often around the feet and ankles, the position of swelling is due to the effects of gravity. Interstitial fluid consists of a solvent containing sugars, salts, fatty acids, amino acids, coenzymes, hormones, neurotransmitters, white blood cells. This water solvent accounts for 26% of the water in the human body, the composition of tissue fluid depends upon the exchanges between the cells in the biological tissue and the blood. This means that tissue fluid has a different composition in different tissues, not all of the contents of the blood pass into the tissue, which means that tissue fluid and blood are not the same
Interstitial fluid
–
This article includes a
list of references, but its sources remain unclear because it has insufficient
inline citations. Please help to
improve this article by
introducing more precise citations. (May 2015)
31.
Intracellular fluid
–
The two main fluid compartments are the intracellular and extracellular compartments. The intracellular compartment is the space within the cells, it is separated from the extracellular compartment by cell membranes. About two thirds of the body water of humans is held in the cells, mostly in the cytosol. The intracellular fluid is all contained inside the cells. Most of this is cytosol, the matrix in which cellular organelles are suspended, the cytosol and organelles together compose the cytoplasm. The cell membranes are the outer barrier, in humans, the intracellular compartment contains on average about 28 litres of fluid, and under ordinary circumstances remains in osmotic equilibrium. It contains moderate quantities of magnesium and sulphate ions, the interstitial, intravascular and transcellular compartments comprise the extracellular compartment. Its extracellular fluid contains about one-third of total body water, the interstitial compartment surrounds tissue cells. It is filled with interstitial fluid, interstitial fluid provides the immediate microenvironment that allows for movement of ions, proteins and nutrients across the cell barrier. This fluid is not static, but is continually being refreshed by the blood capillaries, in the average male human body, the interstitial space has approximately 10.5 litres of fluid. The main intravascular fluid in mammals is blood, a mixture with elements of a suspension, colloid. The blood represents both the intracellular compartment and the extracellular compartment, the other intravascular fluid is lymph. It too represents both the intracellular compartment and the extracellular compartment, the average volume of plasma in the average male is approximately 3.5 liters. The volume of the compartment is regulated in part by hydrostatic pressure gradients. Examples of transcellular spaces include the eye, the nervous system, the peritoneal and pleural cavities. A small amount of fluid, called transcellular fluid, does exist normally in such spaces and they are all very important, yet there is not much of each. For example, there is only about 150 mL of cerebrospinal fluid in the central nervous system at any moment. For example, the fluid is made by various cells of the CNS, mostly the ependymal cells
Intracellular fluid
–
Intracellular fluid content in humans
Intracellular fluid
–
The cytosol is a crowded solution of many different types of molecules that fills much of the volume of cells.
32.
Plasma membrane
–
The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is permeable to ions and organic molecules and controls the movement of substances in. The basic function of the membrane is to protect the cell from its surroundings. It consists of the bilayer with embedded proteins. Cell membranes can be artificially reassembled, Some authors that did not believe that there was a functional permeable boundary at the surface of the cell preferred to use the term plasmalemma to the extern region of the cell. The cell membrane surrounds the cytoplasm of living cells, physically separating the components from the extracellular environment. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, fungi, bacteria, most archaea, and plants also have a cell wall, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane is permeable and able to regulate what enters and exits the cell. The movement of substances across the membrane can be passive, occurring without the input of cellular energy, or active. The membrane also maintains the cell potential, the cell membrane thus works as a selective filter that allows only certain things to come inside or go outside the cell. The cell employs a number of mechanisms that involve biological membranes,1. Passive osmosis and diffusion, Some substances such as carbon dioxide and oxygen, can move across the membrane by diffusion. Because the membrane acts as a barrier for certain molecules and ions, such a concentration gradient across a semipermeable membrane sets up an osmotic flow for the water. Transmembrane protein channels and transporters, Nutrients, such as sugars or amino acids, must enter the cell, such molecules diffuse passively through protein channels such as aquaporins in facilitated diffusion or are pumped across the membrane by transmembrane transporters. Protein channel proteins, also called permeases, are quite specific, recognizing and transporting only a limited food group of chemical substances. Endocytosis, Endocytosis is the process in which cells absorb molecules by engulfing them, the plasma membrane creates a small deformation inward, called an invagination, in which the substance to be transported is captured. The deformation then pinches off from the membrane on the inside of the cell, Endocytosis is a pathway for internalizing solid particles, small molecules and ions, and macromolecules. Endocytosis requires energy and is thus a form of active transport and this is the process of exocytosis
Plasma membrane
–
Illustration of a
Eukaryotic cell membrane
33.
Ion channels
–
Not to be confused with, Ion Television or Ion implantation. Ion channels are present in the membranes of all cells, Ion channels are one of the two classes of ionophoric proteins, along with ion transporters. Their classification as molecules is referred to as channelomics, there are two distinctive features of ion channels that differentiate them from other types of ion transporter proteins, The rate of ion transport through the channel is very high. Ions pass through channels down their electrochemical gradient, which is a function of ion concentration and membrane potential, downhill, Ion channels are located within the membrane of most cells and of many intracellular organelles. They are often described as narrow, water-filled tunnels that allow only ions of a certain size and/or charge to pass through and this characteristic is called selective permeability. The archetypal channel pore is just one or two atoms wide at its narrowest point and is selective for specific species of ion, such as sodium or potassium. However, some channels may be permeable to the passage of more than one type of ion, typically sharing a common charge, ions often move through the segments of the channel pore in single file nearly as quickly as the ions move through free solution. In many ion channels, passage through the pore is governed by a gate, Ion channels are integral membrane proteins, typically formed as assemblies of several individual proteins. Such multi-subunit assemblies usually involve an arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer. For most voltage-gated ion channels, the pore-forming subunit are called the α subunit, while the auxiliary subunits are denoted β, γ, because channels underlie the nerve impulse and because transmitter-activated channels mediate conduction across the synapses, channels are especially prominent components of the nervous system. Indeed, numerous toxins that organisms have evolved for shutting down the nervous systems of predators, in the search for new drugs, ion channels are a frequent target. There are over 300 types of ion channels in a living cell, Ion channels may be classified by the nature of their gating, the species of ions passing through those gates, the number of gates and localization of proteins. Further heterogeneity of ion channels arises when channels with different constitutive subunits give rise to a kind of current. Absence or mutation of one or more of the types of channel subunits can result in loss of function and, potentially. Ion channels may be classified by gating, i. e. what opens, Voltage-gated ion channels open or close depending on the voltage gradient across the plasma membrane, while ligand-gated ion channels open or close depending on binding of ligands to the channel. Voltage-gated ion channels open and close in response to membrane potential, Voltage-gated sodium channels, This family contains at least 9 members and is largely responsible for action potential creation and propagation. The pore-forming α subunits are very large and consist of four repeat domains each comprising six transmembrane segments for a total of 24 transmembrane segments. The members of family also coassemble with auxiliary β subunits
Ion channels
–
Birth of an Idea (2007) by
Julian Voss-Andreae. The sculpture was commissioned by
Roderick MacKinnon based on the molecule's atomic coordinates that were determined by MacKinnon's group in 2001.
Ion channels
–
Schematic diagram of an ion channel. 1 - channel
domains (typically four per channel), 2 - outer vestibule, 3 -
selectivity filter, 4 - diameter of selectivity filter, 5 -
phosphorylation site, 6 -
cell membrane.
34.
Muscle contraction
–
Muscle contraction is the activation of tension-generating sites within muscle fibers. The termination of muscle contraction is followed by muscle relaxation, which is a return of the fibers to their low tension-generating state. Muscle contractions can be described based on two variables, length and tension, a muscle contraction is described as isometric if the muscle tension changes but the muscle length remains the same. In contrast, a muscle contraction is isotonic if muscle length changes, if the muscle length shortens, the contraction is concentric, if the muscle length lengthens, the contraction is eccentric. In natural movements that underlie locomotor activity, muscle contractions are multifaceted as they are able to produce changes in length, therefore, neither length nor tension is likely to remain the same in muscles that contract during locomotor activity. In vertebrates, skeletal muscle contractions are neurogenic as they require synaptic input from neurons to produce muscle contractions. A single motor neuron is able to innervate multiple muscle fibers, once innervated, the protein filaments within each skeletal muscle fiber slide past each other to produce a contraction, which is explained by the sliding filament theory. The contraction produced can be described as a twitch, summation, or tetanus, in skeletal muscles, muscle tension is at its greatest when the muscle is stretched to an intermediate length as described by the length-tension relationship. Unlike skeletal muscle, the contractions of smooth and cardiac muscles are myogenic, the mechanisms of contraction in these muscle tissues are similar to those in skeletal muscle tissues. Muscle contractions can be described based on two variables, force and length, force itself can be differentiated as either tension or load. Muscle tension is the force exerted by the muscle on an object whereas a load is the force exerted by an object on the muscle, when muscle tension changes without any corresponding changes in muscle length, the muscle contraction is described as isometric. If the muscle length changes while muscle tension remains the same, in an isotonic contraction, the muscle length can either shorten to produce a concentric contraction or lengthen to produce an eccentric contraction. Furthermore, if the muscle length shortens, the contraction is concentric, but if the muscle length lengthens, then the contraction is eccentric. In natural movements that underlie locomotor activity, muscle contractions are multifaceted as they are able to produce changes in length, therefore, neither length nor tension is likely to remain constant when the muscle is active during locomotor activity. An isometric contraction of a muscle generates tension without changing length, an example can be found when the muscles of the hand and forearm grip an object, the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped. In isotonic contraction, the tension in the muscle remains constant despite a change in muscle length and this occurs when a muscles force of contraction matches the total load on the muscle. In concentric contraction, muscle tension is sufficient to overcome the load, and this occurs when the force generated by the muscle exceeds the load opposing its contraction. During a concentric contraction, a muscle is stimulated to contract according to the sliding filament theory and this occurs throughout the length of the muscle, generating a force at the origin and insertion, causing the muscle to shorten and changing the angle of the joint
Muscle contraction
–
Top-down view of skeletal muscle
Muscle contraction
–
Muscle length versus isometric force
35.
Hormone
–
Hormones have diverse chemical structures, mainly of 3 classes, eicosanoids, steroids, and amino acid/protein derivatives. The glands that secrete hormones comprise the endocrine signaling system, the term hormone is sometimes extended to include chemicals produced by cells that affect the same cell or nearby cells. Hormones affect distant cells by binding to receptor proteins in the target cell resulting in a change in cell function. When a hormone binds to the receptor, it results in the activation of a signal transduction pathway, Hormone secretion may occur in many tissues. Endocrine glands are the example, but specialized cells in various other organs also secrete hormones. Hormone secretion occurs in response to specific biochemical signals from a range of regulatory systems. Upon secretion, certain hormones, including hormones and catecholamines, are water-soluble and are thus readily transported through the circulatory system. The endocrine system secretes hormones directly into the bloodstream typically into fenestrated capillaries, Hormones with paracrine function diffuse through the interstitial spaces to nearby target tissue. The reaction of the cells may then be recognized by the original hormone-producing cells. This is an example of a negative feedback loop. Hormone cells are typically of a cell type, residing within a particular endocrine gland, such as the thyroid gland, ovaries. Hormones exit their cell of origin via exocytosis or another means of membrane transport, the hierarchical model is an oversimplification of the hormonal signaling process. Different tissue types may also respond differently to the same hormonal signal, the rate of hormone biosynthesis and secretion is often regulated by a homeostatic negative feedback control mechanism. Such a mechanism depends on factors that influence the metabolism and excretion of hormones, thus, higher hormone concentration alone cannot trigger the negative feedback mechanism. Negative feedback must be triggered by overproduction of an effect of the hormone, for example, thyroid-stimulating hormone causes growth and increased activity of another endocrine gland, the thyroid, which increases output of thyroid hormones. To release active hormones quickly into the circulation, hormone biosynthetic cells may produce and these can then be quickly converted into their active hormone form in response to a particular stimulus. Eicosanoids are considered to act as local hormones and they are considered to be local because they possess specific effects on target cells close to their site of formation. They also have a rapid degradation cycle, making sure they do not reach distal sites within the body, most hormones initiate a cellular response by initially binding to either cell membrane associated or intracellular receptors
Hormone
–
Different types of hormones are secreted in the body, with different biological roles and functions.
36.
Homeostasis
–
Each of these variables is controlled by a separate “homeostat”, which, together, maintain life. The concept was described by French physiologist Claude Bernard in 1865, the term cybernetics is applied to technological control systems such as thermostats, which function as homeostats, but is often defined much more broadly than the biological term homeostasis. The word homeostasis uses combining forms of homeo- and -stasis, New Latin from Greek, ὅμοιος homoios, similar and στάσις stasis, standing still, yielding the idea of staying the same. The conceptual origins of homeostasis reach back to the ancient Greek concepts of balance, harmony, equilibrium, following these hypotheses, Hippocrates compared health to the harmonious balance of the elements, and illness and disease to the systematic disharmony of these elements. Cannon published an extrapolation from Bernards 1865 work naming his theory homeostasis, Cannon further posited that threats to homeostasis might originate from the external environment or the internal environment, and could be physical or psychological, as in emotional distress. Cannon identified these negative feedback systems and emphasized that, regardless of the nature of the threat to homeostasis, the metabolic processes of all living organisms can only take place in very specific physical and chemical environments. The conditions vary with each organism, and with whether the chemical processes take place inside the cell or in the bathing the cells in multicellular creatures. However, a great many other homeostats, encompassing many aspects of human physiology, if an entity is homeostatically controlled it does not imply that its value is necessarily absolutely steady in health. Core body temperature is, for instance, regulated by a homeostat with temperature sensors in, amongst others, however the set point of the regulator is regularly reset. For instance, core temperature in humans varies during the course of the day, with the lowest temperatures occurring at night. The temperature regulators set point is readjusted in adult women at the start of the phase of the menstrual cycle. The temperature regulators set point is reset during infections to produce a fever, Homeostasis does not govern every activity in the body. For instance the signal from the sensor to the effector is, of necessity, highly variable in order to information about the direction. Similarly the effector’s response needs to be adjustable to reverse the error – in fact it should be very nearly in proportion to the error that is threatening the internal environment. The sensors send messages via sensory nerves to the medulla oblongata of the brain indicating whether the pressure has fallen or risen. One of the effector organs is the heart rate is stimulated to rise when the arterial blood pressure falls. Thus the heart rate is not homeostatically controlled, but is one of effector responses to errors in the blood pressure. Another example is the rate of sweating, the blood urea concentration is an example
Homeostasis
–
Thermal image of a cold-blooded
tarantula (
ectothermic) on a warm-blooded human hand (
endothermic).
37.
Antidiuretic hormone
–
Vasopressin, also known as antidiuretic hormone, is a neurohypophysial hormone found in most mammals. In most species it contains arginine and is also called arginine vasopressin or argipressin. Its two primary functions are to water in the body and to constrict blood vessels. It also increases peripheral vascular resistance, which in turn increases blood pressure. It plays a key role in homeostasis, by the regulation of water, glucose and it is derived from a preprohormone precursor that is synthesized in the hypothalamus and stored in vesicles at the posterior pituitary. Most of vasopressin is stored in the pituitary to be released into the bloodstream. It has a very short half-life between 16–24 minutes, vasopressin regulates the bodys water retention. It is released from the brain when the body is dehydrated and causes the kidneys to conserve water, thus concentrating the urine, at high concentrations, it also raises blood pressure by inducing moderate vasoconstriction. In addition, it has a variety of effects on the brain, having been found, for example. A very similar substance, lysine vasopressin or lypressin, has the function in pigs and is often used in human therapy. e. This occurs through increased transcription and insertion of water channels into the membrane of distal convoluted tubule. Aquaporins allow water to move down their osmotic gradient and out of the nephron and this effect is mediated by V2 receptors. Vasopressin also increases the concentration of calcium in the collecting duct cells, vasopressin, acting through cAMP, also increases transcription of the aquaporin-2 gene, thus increasing the total number of aquaporin-2 molecules in collecting duct cells. Acute increase of sodium absorption across the loop of henle. This adds to the countercurrent multiplication which aids in water reabsorption later in the distal tubule. Serum osmolarity/osmolality is also affected by vasopressin due to its role in keeping proper electrolytic balance in the blood stream, improper balance can lead to dehydration, alkalosis, acidosis or other life-threatening changes. The hormone ADH is partly responsible for this process by controlling the amount of water the body retains from the kidney when filtering the blood stream, recent evidence suggests that vasopressin may have analgesic effects. The analgesia effects of vasopressin were found to be dependent on both stress and sex, one study has suggested that genetic variation in male humans affects pair-bonding behavior
Antidiuretic hormone
–
Avp is expressed in the periventricular region of the hypothalamus in the adult mouse.
Allen Brain Atlases
Antidiuretic hormone
–
Space-filling model of arginine vasopressin
Antidiuretic hormone
Antidiuretic hormone
38.
Parathyroid hormone
–
It essentially increases blood calcium levels. PTH is a key that unlocks the vault to remove the calcium. In consequence, PTH is vital to health, and health problems that yield too little or too much PTH can wreak havoc in the form of disease, hypocalcaemia. PTH half-life is approximately 4 minutes and it has a molecular mass of approximately 9500 Da. hPTH- crystallizes as a slightly bent, long helical dimer. Analysis reveals that the extended conformation of hPTH- is the likely bioactive conformation. The N-terminal fragment 1-34 of parathyroid hormone has been crystallized and the structure has been refined to 0.9 Å resolution. Parathyroid hormone regulates serum calcium through its effects on bone, kidney, bone resorption is the normal destruction of bone by osteoclasts, which are indirectly stimulated by PTH. Stimulation is indirect since osteoclasts do not have a receptor for PTH, rather, PTH binds to osteoblasts, binding stimulates osteoblasts to increase their expression of RANKL and inhibits their secretion of Osteoprotegerin. Free OPG competitively binds to RANKL as a receptor, preventing RANKL from interacting with RANK. The binding of RANKL to RANK stimulates these osteoclast precursors to fuse, forming new osteoclasts, in the kidney, approximately 250 mmol of calcium ions are filtered into the glomerular filtrate per day. Most of this is reabsorbed from the fluid, leaving about 5 mmol/d to be excreted in the urine. This reabsorption occurs throughout the tubule, except in the segment of the loop of Henle. Circulating parathyroid hormone only influences the reabsorption that occurs in the distal tubules, a more important effect of PTH on the kidney is, however, its inhibition of the reabsorption of phosphate from the tubular fluid, resulting in a decrease in the plasma phosphate concentration. Phosphate ions form water-insoluble salts with calcium, thus, a decrease in the phosphate concentration of the blood plasma increases the amount of calcium that is ionized. A third important effect of PTH on the kidney is its stimulation of the conversion of 25-hydroxy vitamin D into 1, 25-dihydroxy vitamin D and this latter form of vitamin D is the active hormone which stimulates calcium uptake from the intestine. In the intestine, via kidney, PTH enhances the absorption of calcium in the intestine by increasing the production of activated vitamin D, vitamin D activation occurs in the kidney. PTH up-regulates 25-hydroxyvitamin D3 1-alpha-hydroxylase, the responsible for 1-alpha hydroxylation of 25-hydroxy vitamin D. This activated form of vitamin D increases the absorption of calcium by the intestine via calbindin, PTH was one of the first hormones to be shown to use the G-protein, adenylyl cyclase second messenger system
Parathyroid hormone
Parathyroid hormone
–
Parathyroid hormone
Parathyroid hormone
Parathyroid hormone
39.
Blood test
–
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick. Multiple tests for specific blood components are grouped together into one test panel called a blood panel or blood work. Blood tests are used in health care to determine physiological and biochemical states, such as disease, mineral content, pharmaceutical drug effectiveness. Typical clinical blood panels include a basic metabolic panel or a complete blood count, Blood tests are also used in drug tests to detect drug abuse. In some of the United States, a blood test is required before marriage, venipuncture is useful as it is a minimally invasive way to obtain cells and extracellular fluid from the body for analysis. Blood flows throughout the body, acting as a medium which provides oxygen, coincidentally, the state of the bloodstream affects, or is affected by, many medical conditions. For these reasons, blood tests are the most commonly performed medical tests, if only a few drops of blood are needed, a fingerstick is performed instead of drawing blood from a vein. Phlebotomists, laboratory practitioners and nurses are those charged with patient blood extraction, however, in special circumstances, and emergency situations, paramedics and physicians sometimes extract blood. Also, respiratory therapists are trained to extract arterial blood to examine arterial blood gases, a basic metabolic panel measures sodium, potassium, chloride, bicarbonate, blood urea nitrogen, magnesium, creatinine, glucose, and sometimes calcium. Tests focusing on cholesterol levels can determine LDL and HDL cholesterol levels, some tests, such as those that measure glucose or a lipid profile, require fasting eight to twelve hours prior to the drawing of the blood sample. For the majority of tests, blood is obtained from the patients vein. Other specialized tests, such as the blood gas test. While the regular glucose test is taken at a point in time. Blood tests results should always be interpreted using the ranges provided by the laboratory that performed the test, upon completion of a blood test analysis, patients may receive a report with blood test abbreviations. Examples of common blood test abbreviations are shown below, protein electrophoresis Western blot Liver function tests Polymerase chain reaction. DNA profiling is today possible with very small quantities of blood, this is commonly used in forensic science. Northern blot Sexually transmitted diseases Full blood count Hematocrit MCV Mean corpuscular hemoglobin concentration Erythrocyte sedimentation rate Cross-matching, determination of blood type for blood transfusion or transplants Blood cultures are commonly taken if infection is suspected. Positive cultures and resulting sensitivity results are useful in guiding medical treatment
Blood test
–
A
venipuncture performed using a
vacutainer
Blood test
–
Vacutainer blood bottles
Blood test
–
Samples of human blood collected for testing. The
barcodes contain information that is used to identify the individual from whom the sample was taken and the blood test requested.
40.
Medical history
–
Most health encounters will result in some form of history being taken. Medical histories vary in their depth and focus, for example, an ambulance paramedic would typically limit their history to important details, such as name, history of presenting complaint, allergies, etc. In contrast, a history is frequently lengthy and in depth. The information obtained in this way, together with the examination, enables the physician and other health professionals to form a diagnosis. If a diagnosis cannot be made, a diagnosis may be formulated. The treatment plan may include further investigations to clarify the diagnosis. A practitioner typically asks questions to obtain the information about the patient, Identification and demographics, name, age. The chief complaint – the major problem or concern. History of the present illness – details about the complaints, enumerated in the CC, review of systems Systematic questioning about different organ systems Family diseases – especially those relevant to the patients chief complaint. Childhood diseases – this is important in pediatrics. Regular and acute medications Allergies – to medications, food, latex, and other environmental factors Sexual history, obstetric/gynecological history, conclusion & closure History-taking may be comprehensive history taking or iterative hypothesis testing. Computerized history-taking could be a part of clinical decision support systems. Whatever system a specific condition may seem restricted to, all the systems are usually reviewed in a comprehensive history. The review of systems often includes all the systems in the body that may provide an opportunity to mention symptoms or concerns that the individual may have failed to mention in the history. Factors that inhibit a proper medical history taking include physical inability of the patient to communicate with the physician, such as unconsciousness, Medical history taking may also be impaired by various factors impeding a proper doctor-patient relationship, such as transitions to physicians that are unfamiliar to the patient. History taking of issues related to sexual or reproductive medicine may be inhibited by a reluctance of the patient to disclose intimate or uncomfortable information, computer-assisted history taking systems have been available since the 1960s. However, their use remains variable across healthcare delivery systems, one advantage of using computerized systems as an auxiliary or even primary source of medically related information is that patients may be less susceptible to social desirability bias. For example, patients may be likely to report that they have engaged in unhealthy lifestyle behaviors
Medical history
–
Example
41.
Renal function
–
Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the rate of filtered fluid through the kidney. Creatinine clearance rate is the volume of plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to secretion, which can be blocked by cimetidine. In alternative fashion, overestimation by older serum creatinine methods resulted in an underestimation of creatinine clearance, both GFR and CCr may be accurately calculated by comparative measurements of substances in the blood and urine, or estimated by formulas using just a blood test result. The results of tests are used to assess the excretory function of the kidneys. Staging of chronic disease is based on categories of GFR as well as albuminuria. Dosage of drugs that are excreted primarily via urine may need to be modified based on either GFR or creatinine clearance, most doctors use the plasma concentrations of the waste substances of creatinine and urea, as well as electrolytes, to determine renal function. These measures are adequate to determine whether a patient is suffering from kidney disease, however, blood urea nitrogen and creatinine will not be raised above the normal range until 60% of total kidney function is lost. Elevated protein levels in urine mark some kidney disease, the most sensitive marker of proteinuria is elevated urine albumin. Persistent presence of more than 30 mg albumin per gram creatinine in the urine is diagnostic of chronic kidney disease, glomerular filtration rate is the volume of fluid filtered from the renal glomerular capillaries into the Bowmans capsule per unit time. Central to the maintenance of GFR is the differential basal tone of the afferent and efferent arterioles. Glomerular filtration rate is equal to the Clearance Rate when any solute is freely filtered and is neither reabsorbed nor secreted by the kidneys, the rate therefore measured is the quantity of the substance in the urine that originated from a calculable volume of blood. This mass equals the mass filtered at the glomerulus as nothing is added or removed in the nephron, the GFR is typically recorded in units of volume per time, e. g. milliliters per minute mL/min. G F R = Urine Concentration × Urine Flow Plasma Concentration There are several different techniques used to calculate or estimate the glomerular filtration rate, the above formula only applies for GFR calculation when it is equal to the Clearance Rate. The GFR can be determined by injecting inulin or the inulin-analog sinistrin into the plasma, compared to the MDRD formula, the inulin clearance slightly overestimates the glomerular function. In early stage renal disease, the inulin clearance may remain normal due to hyperfiltration in the remaining nephrons, incomplete urine collection is an important source of error in inulin clearance measurement. GFR can be measured using radioactive substances, in particular Chromium-51
Renal function
–
Diagram showing the basic physiologic mechanisms of the kidney
42.
Specific gravity
–
This page is about the measurement using water as a reference. For a general use of gravity, see relative density. See intensive property for the property implied by specific, Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is always water at its densest for liquids. Nonetheless, the temperature and pressure must be specified for both the sample and the reference, pressure is nearly always 1 atm. Temperatures for both sample and reference vary from industry to industry, in British beer brewing, the practice for specific gravity as specified above is to multiply it by 1000. Being a ratio of densities, specific gravity is a dimensionless quantity, Specific gravity varies with temperature and pressure, reference and sample must be compared at the same temperature and pressure or be corrected to a standard reference temperature and pressure. Substances with a gravity of 1 are neutrally buoyant in water. Those with SG greater than 1 are denser than water and will, disregarding surface tension effects and those with an SG less than 1 are less dense than water and will float on it. In scientific work, the relationship of mass to volume is expressed directly in terms of the density of the substance under study. It is in industry where specific gravity finds wide application, often for historical reasons. True specific gravity can be expressed mathematically as, S G true = ρ sample ρ H2 O where ρ sample is the density of the sample, the density of water varies with temperature and pressure as does the density of the sample. So it is necessary to specify the temperatures and pressures at which the densities or weights were determined and it is nearly always the case that measurements are made at 1 nominal atmosphere. For true specific gravity calculations, air pressure must be considered, temperatures are specified by the notation with T s representing the temperature at which the samples density was determined and T r the temperature at which the reference density is specified. For example, SG would be understood to mean that the density of the sample was determined at 20°C and of the water at 4°C. Taking into account different sample and reference temperatures, we note that, while S G H2 O =1.000000, it is also the case that S G H2 O =0.998203 /0.999840 =0.998363. Here, temperature is being specified using the current ITS-90 scale, on the previous IPTS-68 scale, the densities at 20 °C and 4 °C are 0.9982071 and 0.9999720 respectively, resulting in an SG value for water of 0.9982343. For example, in the industry, the Plato table lists sucrose concentration by weight against true SG
Specific gravity
–
Testing specific gravity of fuel.
43.
Exercise
–
Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. Frequent and regular physical exercise boosts the immune system and helps prevent diseases of such as cardiovascular disease, type 2 diabetes. Childhood obesity is a global concern, and physical exercise may help decrease some of the effects of childhood. Some care providers call exercise the miracle or wonder drug—alluding to the variety of benefits that it can provide for many individuals. Aside from the advantages, these benefits may include different social rewards for staying active while enjoying the environment of one’s culture. Many individuals choose to exercise publicly outdoors where they can congregate in groups, socialize, in the United Kingdom two to four hours of light activity are recommended during working hours. The goal of aerobic exercise is to increase cardiovascular endurance, examples of aerobic exercise include cycling, swimming, brisk walking, skipping rope, rowing, hiking, playing tennis, continuous training, and long slow distance training. Anaerobic exercise, which includes strength and resistance training, can firm, strengthen, and tone muscles, as well as improve bone strength, balance, examples of strength moves are push-ups, pull-ups, lunges, and bicep curls using dumbbells. Anaerobic exercise also include training, functional training, eccentric training, Interval training, sprinting. Flexibility exercises stretch and lengthen muscles, activities such as stretching help to improve joint flexibility and keep muscles limber. The goal is to improve the range of motion which can reduce the chance of injury, Physical exercise can also include training that focuses on accuracy, agility, power, and speed. Sometimes the terms dynamic and static are used, dynamic exercises such as steady running, tend to produce a lowering of the diastolic blood pressure during exercise, due to the improved blood flow. Conversely, static exercise can cause the pressure to rise significantly. Some studies indicate that exercise may increase life expectancy and the quality of life. People who participate in moderate to high levels of exercise have a lower mortality rate compared to individuals who by comparison are not physically active. Moderate levels of exercise have been correlated with preventing aging by reducing inflammatory potential, the majority of the benefits from exercise are achieved with around 3500 metabolic equivalent minutes per week. A lack of physical activity causes approximately 6% of the burden of disease from coronary disease, 7% of type 2 diabetes, 10% of breast cancer. Overall, physical inactivity causes 9% of premature mortality worldwide, individuals can increase fitness following increases in physical activity levels
Exercise
–
A
U.S. Marine participates in a
triathlon at
Catoctin Mountain in 2005
Exercise
–
Indian wrestler exercising near
Varanasi
Exercise
–
A common
elliptical training machine
Exercise
–
US Marines exercising on the
USS Bataan
44.
Marathon
–
The marathon is a long-distance running race with an official distance of 42.195 kilometres, usually run as a road race. The event was instituted in commemoration of the run of the Greek soldier Pheidippides, a messenger from the Battle of Marathon to Athens. The marathon was one of the original modern Olympic events in 1896, more than 800 marathons are held throughout the world each year, with the vast majority of competitors being recreational athletes as larger marathons can have tens of thousands of participants. The name Marathon comes from the legend of Philippides or Pheidippides and it is said that he ran the entire distance without stopping and burst into the assembly, exclaiming νενικήκαμεν, before collapsing and dying. Lucian of Samosata also gives the story, but names the runner Philippides, there is debate about the historical accuracy of this legend. In some Herodotus manuscripts, the name of the runner between Athens and Sparta is given as Philippides, in 1879, Robert Browning wrote the poem Pheidippides. Brownings poem, his story, became part of late 19th century popular culture and was accepted as a historic legend. This route, as it existed when the Olympics were revived in 1896, was approximately 40 kilometres long, and this route is considerably shorter, some 35 kilometres, but includes a very steep initial climb of more than 5 kilometres. When the modern Olympics began in 1896, the initiators and organizers were looking for a great popularizing event, the idea of a marathon race came from Michel Bréal, who wanted the event to feature in the first modern Olympic Games in 1896 in Athens. This idea was supported by Pierre de Coubertin, the founder of the modern Olympics. The Greeks staged a race for the Olympic marathon on 10 March 1896 that was won by Charilaos Vasilakos in 3 hours and 18 minutes. The winner of the first Olympic marathon, on 10 April 1896, was Spyridon Louis, the marathon of the 2004 Summer Olympics was run on the traditional route from Marathon to Athens, ending at Panathinaiko Stadium, the venue for the 1896 Summer Olympics. The womens marathon was introduced at the 1984 Summer Olympics and was won by Joan Benoit of the United States with a time of 2 hours 24 minutes and 52 seconds. It has become a tradition for the mens Olympic marathon to be the last event of the athletics calendar, often, the mens marathon medals are awarded during the closing ceremony. The Olympic mens record is 2,06,32, set at the 2008 Summer Olympics by Samuel Kamau Wanjiru of Kenya, the Olympic womens record is 2,23,07, set at the 2012 Summer Olympics by Tiki Gelana of Ethiopia. The mens London 2012 Summer Olympic marathon winner was Stephen Kiprotich of Uganda, per capita, the Kalenjin ethnic group of Rift Valley Province in Kenya has produced a highly disproportionate share of marathon and track-and-field winners. Johnny Hayes victory at the 1908 Summer Olympics contributed to the growth of long-distance running and marathoning in the United States. Later that year, races around the season including the Empire City Marathon held on New Years Day 1909 in Yonkers, New York
Marathon
–
Competitors during the 2007
Berlin Marathon
Marathon
–
Competitors during the 2014 Orlen Warsaw Marathon
Marathon
–
Luc-Olivier Merson 's painting depicting
Pheidippides giving word of victory at the
Battle of Marathon to the people of
Athens
Marathon
–
Burton Holmes ' photograph entitled "1896: Three athletes in training for the marathon at the Olympic Games in Athens".
45.
Triathlon
–
A triathlon is a multiple-stage competition involving the completion of three continuous and sequential endurance disciplines. While many variations of the sport exist, triathlon, in its most popular form, involves swimming, cycling, triathletes compete for fastest overall course completion time, including timed transitions between the individual swim, cycle, and run components. The word triathlon is of Greek origin from τρεῖς or treis, a transition area is set up where the athletes change gear for different segments of the race. This is where the switches from swimming to cycling and cycling to running occur and these areas are used to store bicycles, performance apparel, and any other accessories needed for the next stage of the race. The transition from swim to bike is referred to as T1, the athletes overall time for the race includes time spent in T1 and T2. Transition areas vary in size depending on the number of participants expected, in addition, these areas provide a social headquarters before the race. The nature of the focuses on persistent and often periodized training in each of the three disciplines, as well as combination workouts and general strength conditioning. Triathlon is considered by some to have its beginnings in 1920s France and this race is held every year in France near Joinville-le-Pont, in Meulan and Poissy. An earlier tri-sport event in 1902 featured running, cycling, there are documented tri-sport events featuring running, swimming, & cycling in 1920,1921,1945, and the 1960s. In 1920, the French newspaper L´Auto reported on a competition called Les Trois Sports with a 3 km run,12 km bike, and those three parts were done without any break. Another event was held in 1921 in Marseilles with the order of events bike-run-swim, the first modern swim/bike/run event to be called a triathlon was held at Mission Bay, San Diego, California on September 25,1974. The race was conceived and directed by Jack Johnstone and Don Shanahan, members of the San Diego Track Club, and was sponsored by the track club. It was reportedly not inspired by the French events, although a race the year at Fiesta Island, San Diego. The International Triathlon Union was founded in 1989 as the governing body of the sport, with the chief goal, at that time. In addition, the ITU has a Long Distance Triathlon series, the World Triathlon Corporation is a private company that sanctions and organizes the Ironman and Ironman 70.3 races each year. These races serve as qualifying events for their own annual World Championships, the Ironman World Championship is held annually in Kailua-Kona, Hawaii in October while the Ironman 70.3 World Championship is held in September and changes location each year. The Ironman and Iron brands are property of the WTC, therefore, long-distance multi-sport events organized by groups other than the WTC may not officially be called Ironman or Iron races. For its part, the ITU does not sanction WTC races, however, USAT uses a combination of ITU, the Challenge Family brand produces long-distance events around the world, and includes events like Challenge Roth
Triathlon
–
The three typical components of triathlon: swimming, cycling, and running.
Triathlon
–
The symbol for triathlon in the Olympics
Triathlon
–
Competition and pressure for faster times have led to the development of specialized triathlon clothing that is adequate for both swimming and cycling, such as
speedsuits.
Triathlon
–
Reality TV's "Survivor" winner, Parvati Shallow, dressed to compete in the 2008 Nautica Triathlon Malibu Individual Open for females.
46.
Electrode
–
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit. The word was coined by William Whewell at the request of the scientist Michael Faraday from the Greek words elektron, meaning amber, and hodos, an electrode in an electrochemical cell is referred to as either an anode or a cathode. The anode is now defined as the electrode at which electrons leave the cell and oxidation occurs, each electrode may become either the anode or the cathode depending on the direction of current through the cell. A bipolar electrode is an electrode that functions as the anode of one cell, a primary cell is a special type of electrochemical cell in which the reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode, the cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the reactions are reversible. When the cell is being charged, the anode becomes the positive and this is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a cell, with the anode as the negative. In a vacuum tube or a semiconductor having polarity the anode is the positive electrode, the electrons enter the device through the cathode and exit the device through the anode. Many devices have other electrodes to control operation, e. g. base, gate, control grid. In a three-electrode cell, an electrode, also called an auxiliary electrode, is used only to make a connection to the electrolyte so that a current can be applied to the working electrode. The counter electrode is made of an inert material, such as a noble metal or graphite. In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. Depending upon the process, the electrode is either consumable, in the case of gas metal arc welding or shielded metal arc welding, or non-consumable, such as in gas tungsten arc welding. For a direct current system the weld rod or stick may be a cathode for a filling type weld or an anode for other welding processes, for an alternating current arc welder the welding electrode would not be considered an anode or cathode. Electrodes are used to provide current through nonmetal objects to them in numerous ways. These electrodes are used for advanced purposes in research and investigation
Electrode
–
Electrodes used in
arc welding
47.
Voltage
–
Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against an electric field to move the test charge between two points. This is measured in units of volts, voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or some combination of these three. A voltmeter can be used to measure the voltage between two points in a system, often a reference potential such as the ground of the system is used as one of the points. A voltage may represent either a source of energy or lost, used, given two points in space, x A and x B, voltage is the difference in electric potential between those two points. Electric potential must be distinguished from electric energy by noting that the potential is a per-unit-charge quantity. Like mechanical potential energy, the zero of electric potential can be chosen at any point, so the difference in potential, i. e. the voltage, is the quantity which is physically meaningful. The voltage between point A to point B is equal to the work which would have to be done, per unit charge, against or by the electric field to move the charge from A to B. The voltage between the two ends of a path is the energy required to move a small electric charge along that path. Mathematically this is expressed as the integral of the electric field. In the general case, both an electric field and a dynamic electromagnetic field must be included in determining the voltage between two points. Historically this quantity has also called tension and pressure. Pressure is now obsolete but tension is used, for example within the phrase high tension which is commonly used in thermionic valve based electronics. Voltage is defined so that negatively charged objects are pulled towards higher voltages, therefore, the conventional current in a wire or resistor always flows from higher voltage to lower voltage. Current can flow from lower voltage to higher voltage, but only when a source of energy is present to push it against the electric field. This is the case within any electric power source, for example, inside a battery, chemical reactions provide the energy needed for ion current to flow from the negative to the positive terminal. The electric field is not the only factor determining charge flow in a material, the electric potential of a material is not even a well defined quantity, since it varies on the subatomic scale. A more convenient definition of voltage can be found instead in the concept of Fermi level, in this case the voltage between two bodies is the thermodynamic work required to move a unit of charge between them
Voltage
–
Batteries are sources of voltage in many
electric circuits
Voltage
–
Working on
high voltage power lines
Voltage
–
Multimeter set to measure voltage
48.
Electron
–
The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
Electron
–
A beam of electrons deflected in a circle by a magnetic field
Electron
–
Hydrogen atom
orbitals at different energy levels. The brighter areas are where you are most likely to find an electron at any given time.
Electron
–
Robert Millikan
Electron
–
A
lightning discharge consists primarily of a flow of electrons. The electric potential needed for lightning may be generated by a triboelectric effect.
49.
Cathode
–
A cathode is the electrode from which a conventional current leaves a polarized electrical device. A conventional current describes the direction in which positive electronic charges move, Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic cathode current departs also means that flow into the devices cathode. Cathode polarity with respect to the anode can be positive or negative and this outward current is carried internally by positive ions moving from the electrolyte to the positive cathode. It is continued externally by electrons moving inwards, this negative charge moving inwards constituting positive current flowing outwards, for example, the Daniell galvanic cells copper electrode is the positive terminal and the cathode. In a recharging battery, or an electrolytic cell performing electrolysis, for example, reversing the current direction in a Daniell galvanic cell would produce an electrolytic cell, where the copper electrode is the positive terminal and the anode. In a diode, the cathode is the terminal at the pointed end of the arrow symbol. Note, electrode naming for diodes is always based on the direction of the forward current, an electrode through which current flows the other way is termed an anode. The use of West to mean the out direction may appear unnecessarily contrived, previously, as related in the first reference cited above, Faraday had used the more straightforward term exode. The reference he used to effect was the Earths magnetic field direction. The flow of electrons is almost always from anode to cathode outside of the cell or device, regardless of the cell or device type, an exception is when a diode reverse-conducts, either by accident or by design. In chemistry, a cathode is the electrode of a cell at which reduction occurs. Another mnemonic is to note the cathode has a c, as does reduction, perhaps most useful would be to remember cathode corresponds to cation and anode corresponds to anion. The cathode can be negative like when the cell is electrolytic, the cathode supplies electrons to the positively charged cations which flow to it from the electrolyte. The cathodic current, in electrochemistry, is the flow of electrons from the interface to a species in solution. The anodic current is the flow of electrons into the anode from a species in solution, in an electrolytic cell, the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or pure metal from metal ions, when discussing the relative reducing power of two redox agents, the couple for generating the more reducing species is said to be more cathodic with respect to the more easily reduced reagent. When metal ions are reduced from ionic solution, they form a metal surface on the cathode
Cathode
–
Glow from the directly heated cathode of a 1 kW power
tetrode tube in a radio transmitter. The cathode filament is not directly visible
Cathode
–
Diagram of a
copper cathode in a
galvanic cell (e.g., a battery). A positive current i flows out of the cathode.
Cathode
–
Two indirectly-heated cathodes (orange heater strip) in ECC83 dual triode tube
Cathode
–
Cold cathode (lefthand electrode) in
neon lamp
50.
Anode
–
An anode is an electrode through which conventional current flows into a polarized electrical device. A common mnemonic is ACID for anode current into device, the direction of electric current is opposite to the direction of electron flow, electrons flow out the anode to the outside circuit. The terms anode and cathode do not relate to the polarity of those electrodes but the direction of the current. Conventional current quantifies the flow of positive charge, in most cases, positive charge leaves the device via the cathode, and positive charge flows into the device via the anode. Conventional current depends not only on the direction the charge carriers move, the currents outside the device are usually carried by electrons in a metal conductor. The flow of electrons is opposite to conventional current because electrons have a negative charge, consequently, electrons leave the device via the anode, and electrons enter the device through the cathode. The anode and cathode have slightly different definitions for electrical devices such as diodes and vacuum tubes where the naming is fixed. These devices usually allow substantial current flow in one direction but negligible current in the other direction, consequently, the electrode names use the terms that have substantial ordinary currents. An ideal diode allows current in one direction but not in the other, for the ideal diode, it makes sense to always call that terminal the anode. For non-ideal diodes, the electrodes are also given fixed names even though such a diode under reverse bias would have a positive charge out of the anode. For some operating conditions and devices, such as diode breakdown, Zener diodes, or photodiodes, the polarity of voltage on an anode with respect to an associated cathode varies depending on the device type and on its operating mode. This inward current is carried externally by electrons moving outwards, negative charge flowing in one direction being electrically equivalent to positive charge flowing in the opposite direction. In a recharging battery, or a cell, the anode is the positive terminal. In a diode, the anode is the terminal at the tail of the arrow symbol. Note electrode naming for diodes is always based on the direction of the forward current, in a cathode ray tube, the anode is the positive terminal where electrons flow out of the device, i. e. where positive electric current flows in. The use of East to mean the in direction may appear contrived, previously, as related in the first reference cited above, Faraday had used the more straightforward term eisode. The reference he used to effect was the Earths magnetic field direction. In electrochemistry, the anode is where oxidation occurs and is the positive polarity contact in an electrolytic cell, at the anode, anions are forced by the electrical potential to react chemically and give off electrons which then flow up and into the driving circuit
Anode
–
Sacrificial anodes mounted "on the fly" for corrosion protection of a metal structure
Anode
–
Diagram of a
zinc anode in a
galvanic cell. Note how electrons move out of the cell, and the
conventional current moves into it in the opposite direction.
