1.
Aqueous humour
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The aqueous humour is a transparent, watery fluid similar to plasma, but containing low protein concentrations. It is secreted from the epithelium, a structure supporting the lens. Amino acids, transported by ciliary muscles 98% water Electrolytes Ascorbic acid Glutathione Immunoglobulins Maintains the intraocular pressure and it is this hydrostatic pressure which keeps the eyeball in a roughly spherical shape and keeps the walls of the eyeball taut. Provides nutrition for the avascular ocular tissues, posterior cornea, trabecular meshwork, lens, may serve to transport ascorbate in the anterior segment to act as an antioxidant agent. Presence of immunoglobulins indicate a role in response to defend against pathogens. Provides inflation for expansion of the cornea and thus increased protection against dust, wind, pollen grains, the main eye structures related to aqueous humor dynamics are the ciliary body, and the trabecular meshwork and the uveoscleral pathway. Aqueous humor is secreted into the chamber by the ciliary body. 5 alpha-dihydrocortisol, an enzyme inhibited by 5-alpha reductase inhibitors, may be involved in production of aqueous humor, aqueous humor is continually produced by the ciliary processes and this rate of production must be balanced by an equal rate of aqueous humor drainage. Small variations in the production or outflow of aqueous humour will have an influence on the intraocular pressure. From there, the aqueous humour exits the eye through the trabecular meshwork into Schlemms canal It flows through 25–30 collector canals into the episcleral veins, the greatest resistance to aqueous flow is provided by the trabecular meshwork, and this is where most of the aqueous outflow occurs. The internal wall of the canal is very delicate and allows the fluid to filter due to pressure of the fluid within the eye. The secondary route is the drainage, and is independent of the intraocular pressure, the aqueous flows through here. The fluid is normally 15 mmHg above atmospheric pressure, so when a syringe is injected the fluid flows easily, if the fluid is leaking, due to collapse and wilting of cornea, the hardness of the normal eye is therefore corroborated. Glaucoma is a progressive optic neuropathy where retinal ganglion cells and their axons die causing a corresponding visual field defect, an important risk factor is increased intraocular pressure either through increased production or decreased outflow of aqueous humour. Increased resistance to outflow of aqueous humour may occur due to an abnormal trabecular mesh work or to obliteration of the due to injury or disease of the iris. However, increased pressure is neither sufficient nor necessary for development of primary open angle glaucoma. Uncontrolled glaucoma typically leads to visual field loss and ultimately blindness, archived from the original on 2014-01-01
2.
Solvation shell
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A solvation shell is the solvent interface of any chemical compound or biomolecule that constitutes the solute. When the solvent is water it is referred to as a hydration shell or hydration sphere. A classic example is when water molecules arrange around a metal ion, for example, if the latter were a cation, the electronegative oxygen atom of the water molecule would be attracted electrostatically to the positive charge on the metal ion. The result is a shell of water molecules that surround the ion. This shell can be several thick, dependent upon the charge of the ion, its distribution. The hydration shell that forms around proteins is of importance in biochemistry. This interaction of the surface with the surrounding water is often referred to as protein hydration and is fundamental to the activity of the protein. The hydration layer around a protein has found to have dynamics distinct from the bulk water to a distance of 1 nm. With other solvents and solutes, varying steric and kinetic factors can affect the solvation shell. They result from an incomplete clustering of side-chain nonpolar groups that wrap the polar pair within the protein structure, dehydrons promote the removal of surrounding water through protein associations or ligand binding. Dehydrons can be identified by calculating the reversible work per unit area required to span the aqueous interface of a soluble protein, metal ions in aqueous solution Water model Poisson-Boltzmann equation Hydration energy Solvation London South Bank University pages on protein hydration Journal of Chemical Physics Book
3.
Solution
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In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, 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 characteristics of the solvent when the solvent is the fraction of the mixture. 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, 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. The solute from a solution cannot be separated by filtration and it is composed of only one phase. Homogeneous means that the components of the form a single phase. Heterogeneous means that the components of the mixture are of different phase, the properties of the mixture can be uniformly distributed through the volume but only in absence of diffusion phenomena or after their completion. Usually, the present in the greatest amount is considered the solvent. Solvents can be gases, liquids or solids, one or more components present in the solution other than the solvent are called solutes. The solution has the physical state as the solvent. If the solvent is a gas, only gases are dissolved under a set of conditions. An example of a solution is air. Since interactions between molecules play almost no role, dilute gases form rather trivial solutions, in part of the literature, they are not even classified as solutions, but addressed as mixtures. If the solvent is a liquid, then almost all gases, liquids, 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. Liquid in liquid, The mixing of two or more substances of the same chemistry but different concentrations to form a constant, alcoholic beverages are basically solutions of ethanol in water. Solid in liquid, Sucrose in water Sodium chloride or any other salt in water, solutions in water are especially common. Counterexamples are provided by liquid mixtures that are not homogeneous, colloids, body fluids are examples for complex liquid solutions, containing many solutes
4.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
5.
Chemical equation
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The coefficients next to the symbols and formulae of entities are the absolute values of the stoichiometric numbers. The first chemical equation was diagrammed by Jean Beguin in 1615, a chemical equation consists of the chemical formulas of the reactants and the chemical formula of the products. The two are separated by a symbol and each individual substances chemical formula is separated from others by a plus sign. But, for equations involving complex chemicals, rather than reading the letter and its subscript, using IUPAC nomenclature, this equation would be read as hydrochloric acid plus sodium yields sodium chloride and hydrogen gas. This equation indicates that sodium and HCl react to form NaCl, the stoichiometric coefficients result from the law of conservation of mass and the law of conservation of charge. Symbols are used to differentiate different types of reactions. To denote the type of reaction, = symbol is used to denote a stoichiometric relation, → symbol is used to denote a net forward reaction. ⇄ symbol is used to denote a reaction in both directions, ⇌ symbol is used to denote an equilibrium. The physical state of chemicals is very commonly stated in parentheses after the chemical symbol. When stating physical state, denotes a solid, denotes a liquid, denotes a gas, if the reaction requires energy, it is indicated above the arrow. A capital Greek letter delta is put on the arrow to show that energy in the form of heat is added to the reaction. H ν is used if the energy is added in the form of light, other symbols are used for other specific types of energy or radiation. The law of conservation of mass dictates that the quantity of each element does not change in a chemical reaction, thus, each side of the chemical equation must represent the same quantity of any particular element. Likewise, the charge is conserved in a chemical reaction, therefore, the same charge must be present on both sides of the balanced equation. One balances a chemical equation by changing the number for each chemical formula. Simple chemical equations can be balanced by inspection, that is, by trial, another technique involves solving a system of linear equations. Balanced equations are written with smallest whole-number coefficients, if there is no coefficient before a chemical formula, the coefficient 1 is understood. Looking at the atom, the right-hand side has two atoms, while the left-hand side has four
6.
Chemical formula
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These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
7.
Salt
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Salt is present in vast quantities in seawater, where it is the main mineral constituent. The open ocean has about 35 grams of solids per litre, Salt is essential for life in general, and saltiness is one of the basic human tastes. The tissues of animals contain larger quantities of salt than do plant tissues, Salt is one of the oldest and most ubiquitous food seasonings, and salting is an important method of food preservation. Salt was also prized by the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites, Egyptians, and the Indians. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, the scarcity and universal need for salt has led nations to go to war over it and use it to raise tax revenues. Salt is used in ceremonies and has other cultural significance. Salt is processed from salt mines, or by the evaporation of seawater or mineral-rich spring water in shallow pools. Its major industrial products are caustic soda and chlorine, and is used in industrial processes including the manufacture of polyvinyl chloride, plastics, paper pulp. Of the annual production of around two hundred million tonnes of salt, only about 6% is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use, edible salt is sold in forms such as sea salt and table salt which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency. As well as its use in cooking and at the table, sodium is an essential nutrient for human health via its role as an electrolyte and osmotic solute. Excessive salt consumption can increase the risk of diseases, such as hypertension, in children. Such health effects of salt have long been studied, accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The World Health Organization recommends that adults should consume less than 2,000 mg of sodium, humans have always tended to build communities either around sources of salt, or where they can trade for it. All through history the availability of salt has been pivotal to civilization, the word salary comes from the Latin word for salt because the Roman Legions were sometimes paid in salt. The Natron Valley was a key region that supported the Egyptian Empire to its north, because it supplied it with a kind of salt that came to be called by its name, natron. Even before this, what is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, even the name Solnisata means salt works. A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a spring in Lunca, Neamț County
8.
Solvation
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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
