In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent; the mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution assumes the phase of the solvent when the solvent is the larger fraction of the mixture, as is the case; the concentration of a solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution. The term aqueous solution is. A solution is a homogeneous mixture of two or more substances; the particles of solute in a solution cannot be seen by the naked eye. A solution does not allow beams of light to scatter. A solution is stable; the solute from a solution cannot be separated by filtration. It is composed of only one phase. Homogeneous means. Heterogeneous means; the properties of the mixture can be uniformly distributed through the volume but only in absence of diffusion phenomena or after their completion.
The substance present in the greatest amount is considered the solvent. Solvents can be liquids or solids. One or more components present in the solution other; the solution has the same physical state as the solvent. If the solvent is a gas, only gases are dissolved under a given set of conditions. An example of a gaseous solution is air. Since interactions between molecules play no role, dilute gases form rather trivial solutions. In part of the literature, they are not classified as solutions, but addressed as mixtures. If the solvent is a liquid almost all gases and solids can be dissolved. Here are some examples: Gas in liquid: Oxygen in water Carbon dioxide in water – a less simple example, because the solution is accompanied by a chemical reaction. Note that the visible bubbles in carbonated water are not the dissolved gas, but only an effervescence of carbon dioxide that has come out of solution. Liquid in liquid: The mixing of two or more substances of the same chemistry but different concentrations to form a constant.
Alcoholic beverages are solutions of ethanol in water. Solid in liquid: Sucrose in water Sodium chloride or any other salt in water, which forms an electrolyte: When dissolving, salt dissociates into ions. Solutions in water are common, are called aqueous solutions. Non-aqueous solutions are. Counter examples are provided by liquid mixtures that are not homogeneous: colloids, emulsions are not considered solutions. Body fluids are examples for complex liquid solutions. Many of these are electrolytes. Furthermore, they contain solute molecules like urea. Oxygen and carbon dioxide are essential components of blood chemistry, where significant changes in their concentrations may be a sign of severe illness or injury. If the solvent is a solid gases and solids can be dissolved. Gas in solids: Hydrogen dissolves rather well in metals in palladium. Liquid in solid: Mercury in gold, forming an amalgam Water in solid salt or sugar, forming moist solids Hexane in paraffin wax Solid in solid: Steel a solution of carbon atoms in a crystalline matrix of iron atoms Alloys like bronze and many others Polymers containing plasticizers The ability of one compound to dissolve in another compound is called solubility.
When a liquid can dissolve in another liquid the two liquids are miscible. Two substances that can never mix to form a solution are said to be immiscible. All solutions have a positive entropy of mixing; the interactions between different molecules or ions may be energetically favored or not. If interactions are unfavorable the free energy decreases with increasing solute concentration. At some point the energy loss outweighs the entropy gain, no more solute particles can be dissolved. However, the point at which a solution can become saturated can change with different environmental factors, such as temperature and contamination. For some solute-solvent combinations a supersaturated solution can be prepared by raising the solubility to dissolve more solute, lowering it; the greater the temperature of the solvent, the more of a given solid solute it can dissolve. However, most gases and some compounds exhibit solubilities that decrease with increased temperature; such behavior is a result of an exothermic enthalpy of solution.
Some surfactants exhibit this behaviour. The solubility of liquids in liquids is less temperature-sensitive than that of solids or gases; the physical properties of compounds such as melting point and boiling point change when other compounds are added. Together they are called colligative properties. There are several ways to quantify the amount of one compound dissolved in the other compounds collectively called concentration. Examples include molarity, volume fraction, mole fraction; the properties of ideal solutions can be calculated by the linear combination of the properties of
Protoplast, from ancient Greek πρωτόπλαστος, is a biological term proposed by Hanstein in 1880 to refer to the entire cell, excluding the cell wall, but has several definitions: a plant, bacterial or fungal cell that had its cell wall or removed using either mechanical or enzymatic means. A further differentiation can be made for bacteria: protoplasts: have their cell wall removed and are derived from gram + spheroplasts: have their cell wall only removed and are gram − more a unit of biology, composed of a cell's nucleus and the surrounding protoplasmic materials. Cell walls are made of a variety of polysaccharides. Protoplasts can be made by degrading cell walls with a mixture of the appropriate polysaccharide-degrading enzymes: During and subsequent to digestion of the cell wall, the protoplast becomes sensitive to osmotic stress; this means cell wall digestion and protoplast storage must be done in an isotonic solution to prevent rupture of the plasma membrane. Protoplasts can be used to study membrane biology, including the uptake of macromolecules and viruses.
These are used in somaclonal variation. Protoplasts are used for DNA transformation, since the cell wall would otherwise block the passage of DNA into the cell. In the case of plant cells, protoplasts may be regenerated into whole plants first by growing into a group of plant cells that develops into a callus and by regeneration of shoots from the callus using plant tissue culture methods. Growth of protoplasts into callus and regeneration of shoots requires the proper balance of plant growth regulators in the tissue culture medium that must be customized for each species of plant. Unlike protoplasts from vascular plants, protoplasts from mosses, such as Physcomitrella patens, do not need phytohormones for regeneration, nor do they form a callus during regeneration. Instead, they regenerate directly into the filamentous protonema, mimicking a germinating moss spore. Protoplasts may be used for plant breeding, using a technique called protoplast fusion. Protoplasts from different species are induced to fuse by using an electric field or a solution of polyethylene glycol.
This technique may be used to generate somatic hybrids in tissue culture. Additionally, protoplasts of plants expressing fluorescent proteins in certain cells may be used for Fluorescence Activated Cell Sorting, where only cells fluorescing a selected wavelength are retained. Among other things, this technique is used to isolate specific cell types for further investigations, such as transcriptomics. L-form bacteria
Diffusion is the net movement of molecules or atoms from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in chemical potential of the diffusing species. A gradient is the change in the value of a quantity e.g. concentration, pressure, or temperature with the change in another variable distance. A change in concentration over a distance is called a concentration gradient, a change in pressure over a distance is called a pressure gradient, a change in temperature over a distance is called a temperature gradient; the word diffusion derives from the Latin word, which means "to spread way out.” A distinguishing feature of diffusion is that it depends on particle random walk, results in mixing or mass transport without requiring directed bulk motion. Bulk motion, or bulk flow, is the characteristic of advection; the term convection is used to describe the combination of both transport phenomena. An example of a situation in which bulk motion and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration known as breathing.
The lungs are located in the thoracic cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs, which causes a decrease in pressure in the alveoli; this creates a pressure gradient between the air outside the body at high pressure and the alveoli at low pressure. The air moves down the pressure gradient through the airways of the lungs and into the alveoli until the pressure of the air and that in the alveoli are equal i.e. the movement of air by bulk flow stops once there is no longer a pressure gradient. The air arriving in the alveoli has a higher concentration of oxygen than the “stale” air in the alveoli; the increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli. Oxygen moves by diffusion, down the concentration gradient, into the blood; the other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases.
This creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli, as fresh air has a low concentration of carbon dioxide compared to the blood in the body. The pumping action of the heart transports the blood around the body; as the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a pressure gradient between the heart and the capillaries, blood moves through blood vessels by bulk flow down the pressure gradient; as the thoracic cavity contracts during expiration, the volume of the alveoli decreases and creates a pressure gradient between the alveoli and the air outside the body, air moves by bulk flow down the pressure gradient. The concept of diffusion is used in: physics, biology, sociology and finance. However, in each case, the object, undergoing diffusion is “spreading out” from a point or location at which there is a higher concentration of that object. There are two ways to introduce the notion of diffusion: either a phenomenological approach starting with Fick's laws of diffusion and their mathematical consequences, or a physical and atomistic one, by considering the random walk of the diffusing particles.
In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion. According to Fick's laws, the diffusion flux is proportional to the negative gradient of concentrations, it goes from regions of higher concentration to regions of lower concentration. Sometime various generalizations of Fick's laws were developed in the frame of thermodynamics and non-equilibrium thermodynamics. From the atomistic point of view, diffusion is considered as a result of the random walk of the diffusing particles. In molecular diffusion, the moving molecules are self-propelled by thermal energy. Random walk of small particles in suspension in a fluid was discovered in 1827 by Robert Brown; the theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein. The concept of diffusion is applied to any subject matter involving random walks in ensembles of individuals. Biologists use the terms "net movement" or "net diffusion" to describe the movement of ions or molecules by diffusion.
For example, oxygen can diffuse through cell membranes so long as there is a higher concentration of oxygen outside the cell. However, because the movement of molecules is random oxygen molecules move out of the cell; because there are more oxygen molecules outside the cell, the probability that oxygen molecules will enter the cell is higher than the probability that oxygen molecules will leave the cell. Therefore, the "net" movement of oxygen molecules is into the cell. In other words, there is a net movement of oxygen molecules down the concentration gradient. In the scope of time, diffusion in solids was used. For example, Pliny the Elder had described the cementation process, which produces steel from the element iron through carbon diffusion. Another example is well known for many centuries, the diffusion of colors of stained glass or earthenware and Chinese ceramics. In modern science, the first systematic experimental study of di
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from resin, or cell sap. Saps may be broadly divided into two types: xylem sap and phloem sap. Xylem sap consists of a watery solution of hormones, mineral elements and other nutrients. Transport of sap in xylem is characterized by movement from the roots toward the leaves. Over the past century, there has been some controversy regarding the mechanism of xylem sap transport. Xylem sap transport can be disrupted by cavitation—an "abrupt phase change from liquid to vapor"—resulting in air-filled xylem conduits. In addition to being a fundamental physical limit on tree height, two environmental stresses can disrupt xylem transport by cavitation: "increasingly negative xylem pressures associated with water stress, freeze-thaw cycles in temperate climates. Phloem sap consists of sugars and mineral elements dissolved in water, it flows from where carbohydrates are stored to where they are used.
The pressure flow hypothesis proposes a mechanism for phloem sap transport. Although other hypotheses have been proposed. Phloem sap is thought to play a role in sending informational signals throughout vascular plants. "Loading and unloading patterns are determined by the conductivity and number of plasmodesmata and the position-dependent function of solute-specific, plasma membrane transport proteins. Recent evidence indicates that mobile proteins and RNA are part of the plant's long-distance communication signaling system. Evidence exists for the directed transport and sorting of macromolecules as they pass through plasmodesmata." A large number of insects of the order Hemiptera, feed directly on phloem sap, make it the primary component of their diet. Phloem sap is "nutrient-rich compared with many other plant products and lacking in toxins and feeding deterrents, it is consumed as the dominant or sole diet by a restricted range of animals"; this apparent paradox is explained by the fact that phloem sap is physiologically extreme in terms of animal digestion, it is hypothesized that few animals take direct advantage of this because they lack two adaptations that are necessary to enable direct use by animals.
These include the existence of a high ratio of non-essential/essential amino acids in phloem sap for which these adapted Hemiptera insects contain symbiotic microorganisms which can provide them with essential amino acids. A much larger set of animals do however consume phloem sap by proxy, either "through feeding on the honeydew of phloem-feeding hemipterans. Honeydew is physiologically less extreme than phloem sap, with a higher essential:non-essential amino acid ratio and lower osmotic pressure," or by feeding on the biomass of insects that have grown on more direct ingestion of phloem sap. Maple syrup is made from reduced sugar maple xylem sap; the sap is harvested from the Sugar Maple, Acer saccharum. In some countries harvesting the early spring sap of birch trees for human consumption is common practice. Certain palm tree sap can be used to make palm syrup. In the Canary Islands they use the Canary Island Date Palm while in Chile they use the Chilean Wine Palm to make their syrup called miel de palma.
Actin is a family of globular multi-functional proteins that form microfilaments. It is found in all eukaryotic cells, where it may be present at a concentration of over 100 μM. An actin protein is the monomeric subunit of two types of filaments in cells: microfilaments, one of the three major components of the cytoskeleton, thin filaments, part of the contractile apparatus in muscle cells, it can be present as either a free monomer called G-actin or as part of a linear polymer microfilament called F-actin, both of which are essential for such important cellular functions as the mobility and contraction of cells during cell division. Actin participates in many important cellular processes, including muscle contraction, cell motility, cell division and cytokinesis and organelle movement, cell signaling, the establishment and maintenance of cell junctions and cell shape. Many of these processes are mediated by extensive and intimate interactions of actin with cellular membranes. In vertebrates, three main groups of actin isoforms, alpha and gamma have been identified.
The alpha actins, found in muscle tissues, are a major constituent of the contractile apparatus. The beta and gamma actins coexist in most cell types as components of the cytoskeleton, as mediators of internal cell motility, it is believed that the diverse range of structures formed by actin enabling it to fulfill such a large range of functions is regulated through the binding of tropomyosin along the filaments. A cell's ability to dynamically form microfilaments provides the scaffolding that allows it to remodel itself in response to its environment or to the organism's internal signals, for example, to increase cell membrane absorption or increase cell adhesion in order to form cell tissue. Other enzymes or organelles such as cilia can be anchored to this scaffolding in order to control the deformation of the external cell membrane, which allows endocytosis and cytokinesis, it can produce movement either by itself or with the help of molecular motors. Actin therefore contributes to processes such as the intracellular transport of vesicles and organelles as well as muscular contraction and cellular migration.
It therefore plays an important role in embryogenesis, the healing of wounds and the invasivity of cancer cells. The evolutionary origin of actin can be traced to prokaryotic cells. Actin homologs from prokaryotes and archaea polymerize into different helical or linear filaments consisting of one or multiple strands; however the in-strand contacts and nucleotide binding sites are preserved in prokaryotes and in archaea. Lastly, actin plays an important role in the control of gene expression. A large number of illnesses and diseases are caused by mutations in alleles of the genes that regulate the production of actin or of its associated proteins; the production of actin is key to the process of infection by some pathogenic microorganisms. Mutations in the different genes that regulate actin production in humans can cause muscular diseases, variations in the size and function of the heart as well as deafness; the make-up of the cytoskeleton is related to the pathogenicity of intracellular bacteria and viruses in the processes related to evading the actions of the immune system.
Actin was first observed experimentally in 1887 by W. D. Halliburton, who extracted a protein from muscle that'coagulated' preparations of myosin that he called "myosin-ferment". However, Halliburton was unable to further refine his findings, the discovery of actin is credited instead to Brunó Ferenc Straub, a young biochemist working in Albert Szent-Györgyi's laboratory at the Institute of Medical Chemistry at the University of Szeged, Hungary. In 1942, Straub developed a novel technique for extracting muscle protein that allowed him to isolate substantial amounts of pure actin. Straub's method is the same as that used in laboratories today. Szent-Gyorgyi had described the more viscous form of myosin produced by slow muscle extractions as'activated' myosin, since Straub's protein produced the activating effect, it was dubbed actin. Adding ATP to a mixture of both proteins causes a decrease in viscosity; the hostilities of World War II meant Szent-Gyorgyi and Straub were unable to publish the work in Western scientific journals.
Actin therefore only became well known in the West in 1945, when their paper was published as a supplement to the Acta Physiologica Scandinavica. Straub continued to work on actin, in 1950 reported that actin contains bound ATP and that, during polymerization of the protein into microfilaments, the nucleotide is hydrolyzed to ADP and inorganic phosphate. Straub suggested that the transformation of ATP-bound actin to ADP-bound actin played a role in muscular contraction. In fact, this is true only in smooth muscle, was not supported through experimentation until 2001; the amino acid sequencing of actin was completed by M. Elzinga and co-workers in 1973; the crystal structure of G-actin was solved in 1990 by colleagues. In the same year, a model for F-actin was proposed by Holmes and colleagues following experiments using co-crystallization with different proteins; the procedure of co-crystallization with different proteins was used during the following years, until in 2001 the isolated protein was crystallized along with ADP.
However, there is still no high-resolution X-ray structure of F-actin. The crystallization of F-actin was possible due to the use of a rhodamine conjugate that impedes polymerization by blocking the amino acid cys-374. Christine
Botany called plant science, plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist; the term "botany" comes from the Ancient Greek word βοτάνη meaning "pasture", "grass", or "fodder". Traditionally, botany has included the study of fungi and algae by mycologists and phycologists with the study of these three groups of organisms remaining within the sphere of interest of the International Botanical Congress. Nowadays, botanists study 410,000 species of land plants of which some 391,000 species are vascular plants, 20,000 are bryophytes. Botany originated in prehistory as herbalism with the efforts of early humans to identify – and cultivate – edible and poisonous plants, making it one of the oldest branches of science. Medieval physic gardens attached to monasteries, contained plants of medical importance, they were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards.
One of the earliest was the Padua botanical garden. These gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy, led in 1753 to the binomial system of Carl Linnaeus that remains in use to this day. In the 19th and 20th centuries, new techniques were developed for the study of plants, including methods of optical microscopy and live cell imaging, electron microscopy, analysis of chromosome number, plant chemistry and the structure and function of enzymes and other proteins. In the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including genomics and proteomics and DNA sequences to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with inputs from most other areas of science and technology. Research topics include the study of plant structure and differentiation, reproduction and primary metabolism, chemical products, diseases, evolutionary relationships and plant taxonomy.
Dominant themes in 21st century plant science are molecular genetics and epigenetics, which are the mechanisms and control of gene expression during differentiation of plant cells and tissues. Botanical research has diverse applications in providing staple foods, materials such as timber, rubber and drugs, in modern horticulture and forestry, plant propagation and genetic modification, in the synthesis of chemicals and raw materials for construction and energy production, in environmental management, the maintenance of biodiversity. Botany originated as the study and use of plants for their medicinal properties. Many records of the Holocene period date early botanical knowledge as far back as 10,000 years ago; this early unrecorded knowledge of plants was discovered in ancient sites of human occupation within Tennessee, which make up much of the Cherokee land today. The early recorded history of botany includes many ancient writings and plant classifications. Examples of early botanical works have been found in ancient texts from India dating back to before 1100 BC, in archaic Avestan writings, in works from China before it was unified in 221 BC.
Modern botany traces its roots back to Ancient Greece to Theophrastus, a student of Aristotle who invented and described many of its principles and is regarded in the scientific community as the "Father of Botany". His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to botanical science until the Middle Ages seventeen centuries later. Another work from Ancient Greece that made an early impact on botany is De Materia Medica, a five-volume encyclopedia about herbal medicine written in the middle of the first century by Greek physician and pharmacologist Pedanius Dioscorides. De Materia Medica was read for more than 1,500 years. Important contributions from the medieval Muslim world include Ibn Wahshiyya's Nabatean Agriculture, Abū Ḥanīfa Dīnawarī's the Book of Plants, Ibn Bassal's The Classification of Soils. In the early 13th century, Abu al-Abbas al-Nabati, Ibn al-Baitar wrote on botany in a systematic and scientific manner. In the mid-16th century, "botanical gardens" were founded in a number of Italian universities – the Padua botanical garden in 1545 is considered to be the first, still in its original location.
These gardens continued the practical value of earlier "physic gardens" associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much to northern Europe. Throughout this period, botany remained subordinate to medicine. German physician Leonhart Fuchs was one of "the three German fathers of botany", along with theologian Otto Brunfels and physician Hieronymus Bock. Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification. Physician Valerius Cordus authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium
Eduard Adolf Strasburger was a Polish-German professor and one of the most famous botanists of the 19th century. Eduard Strasburger was born in son of Edward Bogumił Strasburger. In 1870, he married Aleksandra Julia Wertheim, had two children: Anna and Julius. Strasburger studied biological sciences in Paris and Jena, receiving a PhD in 1866 after working with Nathanael Pringsheim. In 1868 he taught at the University of Warsaw. In 1869 he was appointed professor of botany at the University of Jena. From 1881 he was head of the Botanisches Institut at the University of Bonn. Strasburger died in Germany. Strasburger was a founder of the famous Lehrbuch der Botanik für Hochschulen, which first appeared in 1894, he was the first to provide an accurate description of the embryonic sac in gymnosperms and angiosperms, along with demonstrating double-fertilization in angiosperms. He came up with one of the modern laws of plant cytology: "New cell nuclei can only arise from the division of other nuclei."
And originated the terms cytoplasm and nucleoplasm. Together with Walther Flemming and Edouard van Beneden, he elucidated chromosome distribution during cell division, his work on the upward movement of tree sap proved that the process was physical and not physiological. He was awarded the Linnean Medal in 1905, as well as the Linnean Society of London's more prestigious Darwin-Wallace Medal in 1908, awarded only once every 50 years. Strasburger was married to the pianist Alexandra Julie Wertheim, his son was the internist Julius Strasburger, a grandson was the ancient historian Hermann Strasburger. On Cell Formation and Cell Division, 1876 – a book in which he set forth the basic principles of mitosis. Ueber das Verhalten des Pollens und die Befruchtungsvorgänge bei den Gymnospermen: Schwärmsporen, pflanzliche Spermatozoiden und das Wesen der Befruchtung. Gustav Fischer Verlag, Jena, 1892. Lehrbuch der Botanik für Hochschulen, 1st ed. 1894. Translated to English, Italian, Polish, Serbo-Croatian, Spanish.
A complete list of editions and translations up to 1994 is given in al.. A Textbook of botany, 1st ed. 1898, English translation of the 2nd German ed. available at BHL. Macmillan, London. Das kleine botanische Practicum für Anfänger: Anleitung zum Selbststudium der mikroskopischen Botanik und Einführung in die mikroskopische Technik, 4th ed. 1902, digital edition by ULB Düsseldorf. List of Poles "Strasburger, Eduard Adolf" Encyclopædia Britannica "Science is in a Constant Flow": Live and Work of Eduard Strasburger Family Tree maintained by great-great-grandniece Elonka Dunin Deutsches Geschlechterbuch Band 207. C. A. Starke Verlag, Limburg an der Lahn. 1998. P. 527 pages. Strasburger, Eduard. A Text-book of Botany. Translated by Hobart Charles Porter. Macmillan Publishers. P. 632 pages. Works by Eduard Strasburger at Project Gutenberg Works by or about Eduard Strasburger at Internet Archive