1.
Cellulose
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Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β linked D-glucose units. Cellulose is an important structural component of the cell wall of green plants, many forms of algae. Some species of bacteria secrete it to form biofilms, Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fiber is 90%, that of wood is 40–50%, Cellulose is mainly used to produce paperboard and paper. Smaller quantities are converted into a variety of derivative products such as cellophane. Conversion of cellulose from energy crops into biofuels such as ethanol is under investigation as an alternative fuel source. Cellulose for industrial use is mainly obtained from wood pulp and cotton, some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In humans, cellulose acts as a bulking agent for feces and is often referred to as a dietary fiber. Cellulose was discovered in 1838 by the French chemist Anselme Payen, Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon from cellulose began in the 1890s and cellophane was invented in 1912, hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized in 1992, by Kobayashi, Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30 degrees, is insoluble in water and most organic solvents, is chiral and is biodegradable. It was shown to melt at 467 °C in 2016 and it can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature. Cellulose is derived from D-glucose units, which condense through β-glycosidic bonds and this linkage motif contrasts with that for α-glycosidic bonds present in starch and glycogen. This confers tensile strength in cell walls, where cellulose microfibrils are meshed into a polysaccharide matrix, compared to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water, cellulose requires a temperature of 320 °C, several different crystalline structures of cellulose are known, corresponding to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures Iα and Iβ, Cellulose produced by bacteria and algae is enriched in Iα while cellulose of higher plants consists mainly of Iβ. Cellulose in regenerated cellulose fibers is cellulose II, the conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III, many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule
2.
Beta-glucan
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Various studies have examined the potential health effects of β-glucan. Oat fiber β-glucan at intake levels of at least 3 g per day can decrease the levels of saturated fats in the blood, some studies have suggested that cereal-derived β-glucan may also have immunomodulatory properties. Yeast- and medicinal mushroom-derived β-glucans have been investigated for their ability to modulate the immune system, β-glucans are further used in various nutraceutical and cosmetic products, as texturing agents, and as soluble fiber supplements, but can be problematic in the process of brewing. Cereal and fungal products have been used for centuries for medicinal and cosmetic purposes, however, β-glucans were first discovered in lichens, and shortly thereafter in barley. A particular interest in oat β-glucan arose after their cholesterol lowering effect was reported in 1984, in 1997, the FDA approved of a claim that intake of at least 3 g of β-glucan from oats per day decreased saturated fats and reduced the risk of heart disease. Although technically β-glucans are chains of D-glucose polysaccharides linked by glycosidic bonds. Cellulose is not typically considered a β-glucan, as it is insoluble, some β-glucan molecules have branching glucose side-chains attached to other positions on the main D-glucose chain, which branch off the β-glucan backbone. In addition, these side-chains can be attached to other types of molecules, like proteins, the most common forms of β-glucans are those comprising D-glucose units with β-1,3 links. Yeast and fungal β-glucans contain 1-6 side branches, while cereal β-glucans contain both β-1,3 and β-1,4 backbone bonds, the frequency, location, and length of the side-chains may play a role in immunomodulation. Differences in molecular weight, shape, and structure of β-glucans dictate the differences in biological activity, β-glucans form a natural component of the cell walls of bacteria, fungi, yeast, and cereals such as oat and barley. Each type of beta-glucan comprises a different molecular backbone, level of branching, one of the most common sources of βD-glucan for supplement use is derived from the cell wall of baker’s yeast. The βD-glucans from yeast are often insoluble, however, β-glucans are also extracted from the bran of some grains, such as oats and barley, and to a much lesser degree in rye and wheat. Other sources include some types of seaweed, and various species of mushrooms, such as reishi, Ganoderma applanatum, shiitake, Chaga, cereal β-glucans from oat, barley, wheat, and rye induce a variety of physiological effects that positively impact health. Barley and oat β-glucans have been studied for their effects on blood glucose regulation in test subjects with hypercholesterolemia, oats and barley differ in the ratio of trimer and tetramer 1-4 linkages. Barley has more 1-4 linkages with a degree of higher than 4. However, the majority of barley blocks remain trimers and tetramers, in oats, β-glucan is found mainly in the endosperm of the oat kernel, especially in the outer layers of that endosperm. β-D-Glucan forms part of the wall of certain medically important fungi. Mushroom beta-glucans are linked by 1,3 glycosidic bonds with 1,6 branches, an assay to detect its presence in blood is marketed as a means of diagnosing invasive fungal infection in patients
3.
Amylose
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Amylose is a helical polymer made of α-D-glucose units, bonded to each other through α glycosidic bonds. This polysaccharide is one of the two components of starch, making up approximately 20-30% of the structure, the other component is amylopectin, which makes up 70–80% of the structure. Amylose is made up of α bound glucose molecules, the carbon atoms on glucose are numbered, starting at the aldehyde carbon, so, in amylose, the 1-carbon on one glucose molecule is linked to the 4-carbon on the next glucose molecule. The structural formula of amylose is pictured at right, the number of repeated glucose subunits is usually in the range of 300 to 3000, but can be many thousands. There are three forms of amylose chains can take. It can exist in a disordered amorphous conformation or two different helical forms and it can bind with itself in a double helix, or it can bind with another hydrophobic guest molecule such as iodine, a fatty acid, or an aromatic compound. This is known as the V form and is how amylopectin binds to amylose to form starch, within this group, there are many different variations. Each is notated with V and then a subscript indicating the number of units per turn. The most common is the V6 form, which has six glucose units a turn, v8 and possibly V7 forms exist as well. These provide a larger space for the guest molecule to bind. This linear structure can have some rotation around the phi and psi angles, because the long linear chains of amylose more readily crystallize than amylopectin, high-amylose starch is more resistant to digestion. Unlike amylopectin, amylose is not soluble in cold water and it also reduces the crystallinity of amylopectin and how easily water can infiltrate the starch. The higher the content, the less expansion potential and the lower the gel strength for the same starch concentration. This can be countered partially by increasing the granule size, fiber X-ray diffraction analysis coupled with computer-based structure refinement has found A-, B-, and C- polymorphs of amylose. Each form corresponds to either the A-, the B-, or the C- starch forms, Amylose is important in plant energy storage. It is less readily digested than amylopectin, however, because it is more linear than amylopectin, as a result, it is the preferred starch for storage in plants. It makes up about 30% of the starch in plants. The digestive enzyme α-amylase is responsible for the breakdown of the molecule into maltotriose and maltose
4.
Polymer
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A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure, Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. The units composing polymers derive, actually or conceptually, from molecules of low molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, Polymers are studied in the fields of biophysics and macromolecular science, and polymer science. Polyisoprene of latex rubber is an example of a polymer. In biological contexts, essentially all biological macromolecules—i. e, proteins, nucleic acids, and polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e. g. Isoprenylated/lipid-modified glycoproteins, where small molecules and oligosaccharide modifications occur on the polyamide backbone of the protein. The simplest theoretical models for polymers are ideal chains, Polymers are of two types, Natural polymeric materials such as shellac, amber, wool, silk and natural rubber have been used for centuries. A variety of natural polymers exist, such as cellulose. Most commonly, the continuously linked backbone of a used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene, whose repeating unit is based on ethylene monomer, however, other structures do exist, for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also present in polymer backbones, such as those of polyethylene glycol, polysaccharides. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network, during the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester, the distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization. However, some methods such as plasma polymerization do not fit neatly into either category
5.
Starch
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Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as an energy store and it is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize, rice, and cassava. Pure starch is a white, tasteless and odorless powder that is insoluble in water or alcohol. It consists of two types of molecules, the linear and helical amylose and the branched amylopectin, depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen, the store of animals, is a more branched version of amylopectin. In industry, starch is converted into sugars, for example by malting and it is processed to produce many of the sugars used in processed foods. Dissolving starch in water gives wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process, starch can be applied to parts of some garments before ironing, to stiffen them. The word starch is from a Germanic root with the strong, stiff. Amylum for starch is from the Greek αμυλον, amylon which means not ground at a mill, the root amyl is used in biochemistry for several compounds related to starch. Starch grains from the rhizomes of Typha as flour have been identified from grinding stones in Europe dating back to 30,000 years ago, starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste was used in Ancient Egypt possibly to glue papyrus, the extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79. Romans used it also in cosmetic creams, to powder the hair, persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in production in China. In addition to starchy plants consumed directly,66 million tonnes of starch were being produced per year world-wide by 2008. In the EU this was around 8.5 million tonnes, with around 40% being used for applications and 60% for food uses. Most green plants use starch as their energy store, an exception is the family Asteraceae, where starch is replaced by the fructan inulin. In photosynthesis, plants use light energy to produce glucose from carbon dioxide, the glucose is used to make cellulose fibers, the structural component of the plant, or is stored in the form of starch granules, in amyloplasts
6.
Amylopectin
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Amylopectin /ˌæmᵻloʊˈpɛktᵻn/ is a water soluble polysaccharide and highly branched polymer of glucose found in plants. It is one of the two components of starch, the other being amylose, glucose units are linked in a linear way with α glycosidic bonds. Branching takes place with α bonds occurring every 24 to 30 glucose units, in contrast, amylose contains very few α bonds, or even none at all. This causes amylose to be hydrolyzed more slowly, but have higher density and its counterpart in animals is glycogen, which has the same composition and structure, but with more extensive branching that occurs every eight to 12 glucose units. Plants store starch within specialized organelles called amyloplasts, when energy is needed for cell work, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, starch is made of about 70% amylopectin by weight, though it varies depending on the source. Amylopectin is highly branched, being formed of 2,000 to 200,000 glucose units and its inner chains are formed of 20-24 glucose subunits. Dissolved amylopectin starch has a tendency of retrogradation during storage. For this main reason, the starches are used in different applications mainly as a thickening agent or stabilizer
7.
Carbohydrate
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A carbohydrate is a biological molecule consisting of carbon, hydrogen and oxygen atoms, usually with a hydrogen–oxygen atom ratio of 2,1, in other words, with the empirical formula Cmn. This formula holds true for monosaccharides, some exceptions exist, for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. Carbohydrates are technically hydrates of carbon, structurally it is accurate to view them as polyhydroxy aldehydes and ketones. The term is most common in biochemistry, where it is a synonym of saccharide, a group that includes sugars, starch, the saccharides are divided into four chemical groups, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest carbohydrates, are referred to as sugars. The word saccharide comes from the Greek word σάκχαρον, meaning sugar, while the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, grape sugar is the glucose, cane sugar is the disaccharide sucrose. Carbohydrates perform numerous roles in living organisms, polysaccharides serve for the storage of energy and as structural components. The 5-carbon monosaccharide ribose is an important component of coenzymes and the backbone of the genetic molecule known as RNA, the related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the system, fertilization, preventing pathogenesis, blood clotting. In food science and in informal contexts, the term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch or simple carbohydrates. Often in lists of information, such as the USDA National Nutrient Database, the term carbohydrate is used for everything other than water, protein, fat, ash. This will include chemical compounds such as acetic or lactic acid, carbohydrates are found in wide variety of foods. The important sources are cereals, potatoes, sugarcane, fruits, table sugar, bread, milk, starch and sugar are the important carbohydrates in our diet. Starch is abundant in potatoes, maize, rice and other cereals, sugar appears in our diet mainly as sucrose which is added to drinks and many prepared foods such as jam, biscuits and cakes. Glucose and fructose are found naturally in fruits and some vegetables. Glycogen is carbohydrate found in the liver and muscles, cellulose in the cell wall of all plant tissue is a carbohydrate. It is important in our diet as fibre which helps to maintain a healthy digestive system, formerly the name carbohydrate was used in chemistry for any compound with the formula Cm n
8.
Monosaccharide
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Monosaccharides, also called simple sugars, are the most basic units of carbohydrates. They are fundamental units of carbohydrates and cannot be hydrolyzed to simpler compounds. The general formula is CnH 2nOn and they are the simplest form of sugar and are usually colorless, water-soluble, and crystalline solids. Some monosaccharides have a sweet taste, examples of monosaccharides include glucose, fructose and galactose. Monosaccharides are the blocks of disaccharides and polysaccharides. Further, each carbon atom that supports a group is chiral, giving rise to a number of isomeric forms. For instance, galactose and glucose are both aldohexoses, but have different physical structures and chemical properties, with few exceptions, monosaccharides have this chemical formula, Cxy, where conventionally x ≥3. Monosaccharides can be classified by the x of carbon atoms they contain, triose tetrose, pentose, hexose, heptose. The most important monosaccharide, glucose, is a hexose, examples of heptoses include the ketoses mannoheptulose and sedoheptulose. Monosaccharides with eight or more carbons are rarely observed as they are quite unstable, in aqueous solutions monosaccharides exist as rings. Simple monosaccharides have a linear and unbranched carbon skeleton with one carbonyl functional group, therefore, the molecular structure of a simple monosaccharide can be written as HnmH, where n +1 + m = x, so that its elemental formula is CxH2xOx. By convention, the atoms are numbered from 1 to x along the backbone. If the carbonyl is at position 1, the molecule begins with a formyl group H− and is technically an aldehyde, in that case, the compound is termed an aldose. Otherwise, the molecule has a group, a carbonyl −− between two carbons, then it is formally a ketone, and is termed a ketose. Ketoses of biological interest usually have the carbonyl at position 2, the various classifications above can be combined, resulting in names such as aldohexose and ketotriose. A more general nomenclature for open-chain monosaccharides combines a Greek prefix to indicate the number of carbons with the suffixes -ose for aldoses, in the latter case, if the carbonyl is not at position 2, its position is then indicated by a numeric infix. So, for example, H4H is pentose, H3H is pentulose, two monosaccharides with equivalent molecular graphs may still be distinct stereoisomers, whose molecules differ in the three-dimensional arrangement of the bonds of certain atoms. This happens only if the molecule contains a center, specifically a carbon atom that is chiral
9.
Glycosidic bond
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In chemistry, a glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide and the group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside, glycosidic bonds of the form discussed above are known as O-glycosidic bonds, in reference to the glycosidic oxygen that links the glycoside to the aglycone or reducing end sugar. In analogy, one also considers S-glycosidic bonds, where the oxygen of the bond is replaced with a sulfur atom. In the same way, N-glycosidic bonds, have the glycosidic oxygen replaced with nitrogen. Substances containing N-glycosidic bonds are known as glycosylamines. C-glycosyl bonds have the oxygen replaced by a carbon, the term C-glycoside is considered a misnomer by IUPAC and is discouraged. All of these modified glycosidic bonds have different susceptibility to hydrolysis, one distinguishes between α- and β-glycosidic bonds based on the relative stereochemistry of the anomeric position and the stereocenter furthest from C1 in the saccharide. An α-glycosidic bond is formed when both carbons have the same stereochemistry, whereas a β-glycosidic bond occurs when the two carbons have different stereochemistry. One complicating issue is that the alpha and beta conformations were originally defined based on the orientation of the major constituents in a Haworth projection. In this case, for D-sugars, a beta conformation would see the major constituent at each carbon drawn above the plane of the ring, for L-sugars, the definitions would then, necessarily, reverse. This is worth noting as these older definitions still permeate the literature, pharmacologists often join substances to glucuronic acid via glycosidic bonds in order to increase their water solubility, this is known as glucuronidation. Many other glycosides have important physiological functions, Nüchter et al. have shown a new approach to Fischer Glycosylation. Employing a microwave oven equipped with refluxing apparatus in a reactor with pressure bombs, Nüchter et al. were able to achieve 100% yield of α-. This method can be performed on a multi-kilogram scale, ondruschka, and W. Lautenschläger, Synthetic Communications 31,1277. Vishal Y Joshis method Joshi et al, d-glucose is first protected by forming the peracetate by addition of acetic anhydride in acetic acid, and then addition of hydrogen bromide which brominates at the 5-position. On addition of the alcohol ROH and lithium carbonate, the OR replaces the bromine and it was suggested by Joshi et al. that lithium acts as the nucleophile that attacks the carbon at the 5-position and through a transition state the alcohol is substituted for the bromine group. Glycoside hydrolases, are enzymes that break glycosidic bonds, glycoside hydrolases typically can act either on α- or on β-glycosidic bonds, but not on both
10.
Hydrolysis
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Hydrolysis usually means the cleavage of chemical bonds by the addition of water. When a carbohydrate is broken into its component sugar molecules by hydrolysis, generally, hydrolysis or saccharification is a step in the degradation of a substance. Hydrolysis can be the reverse of a reaction in which two molecules join together into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water, usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both substance and water molecule to split into two parts, in such reactions, one fragment of the target molecule gains a hydrogen ion. A common kind of hydrolysis occurs when a salt of an acid or weak base is dissolved in water. Water spontaneously ionizes into hydroxide anions and hydronium cations, the salt also dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions, sodium ions react very little with the hydroxide ions whereas the acetate ions combine with hydronium ions to produce acetic acid. In this case the net result is an excess of hydroxide ions. For example, dissolving sulfuric acid in water is accompanied by hydrolysis to give hydronium and bisulfate, for a more technical discussion of what occurs during such a hydrolysis, see Brønsted–Lowry acid–base theory. Acid–base-catalysed hydrolyses are very common, one example is the hydrolysis of amides or esters and their hydrolysis occurs when the nucleophile attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water, in acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups, perhaps the oldest commercially practiced example of ester hydrolysis is saponification. It is the hydrolysis of a triglyceride with a base such as sodium hydroxide. During the process, glycerol is formed, and the fatty acids react with the base and these salts are called soaps, commonly used in households. In addition, in living systems, most biochemical reactions take place during the catalysis of enzymes, the catalytic action of enzymes allows the hydrolysis of proteins, fats, oils, and carbohydrates. As an example, one may consider proteases and they catalyse the hydrolysis of interior peptide bonds in peptide chains, as opposed to exopeptidases. However, proteases do not catalyse the hydrolysis of all kinds of proteins and their action is stereo-selective, Only proteins with a certain tertiary structure are targeted as some kind of orienting force is needed to place the amide group in the proper position for catalysis
11.
Glycogen
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Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in humans, animals, and fungi. The polysaccharide structure represents the main form of glucose in the body. In humans, glycogen is made and stored primarily in the cells of the liver, glycogen functions as the secondary long-term energy storage, with the primary energy stores being fats held in adipose tissue. Muscle glycogen is converted into glucose by muscle cells, and liver glycogen converts to glucose for use throughout the body including the nervous system. Glycogen is the analogue of starch, a polymer that functions as energy storage in plants. It has a similar to amylopectin, but is more extensively branched. Both are white powders in their dry state, glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms a reserve that can be quickly mobilized to meet a sudden need for glucose. In the liver, glycogen can make up from 5–6% of the fresh weight. Only the glycogen stored in the liver can be accessible to other organs. In the muscles, glycogen is found in a low concentration, the amount of glycogen stored in the body—especially within the muscles, liver, and red blood cells—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are found in the kidneys, and even smaller amounts in certain cells in the brain. The uterus also stores glycogen during pregnancy to nourish the embryo, glycogen is a branched biopolymer consisting of linear chains of glucose residues with further chains branching off every 8 to 12 glucoses or so. Glucoses are linked together linearly by α glycosidic bonds from one glucose to the next, branches are linked to the chains from which they are branching off by α glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain. Due to the way glycogen is synthesised, every glycogen granule has at its core a glycogenin protein. Glycogen in muscle, liver, and fat cells is stored in a hydrated form, as a meal containing carbohydrates or protein is eaten and digested, blood glucose levels rise, and the pancreas secretes insulin. Blood glucose from the vein enters liver cells. Insulin acts on the hepatocytes to stimulate the action of several enzymes, glucose molecules are added to the chains of glycogen as long as both insulin and glucose remain plentiful
12.
Chitin
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Chitin n is a long-chain polymer of an N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. The structure of chitin is comparable to the cellulose, forming crystalline nanofibrils or whiskers. In terms of function, it may be compared to the protein keratin, chitin has proved versatile for several medicinal, industrial and biotechnological purposes. The English word chitin comes from the French word chitine, which first appeared in 1821 and derived from the Greek word χιτών, a similar word, chiton, refers to a marine animal with a protective shell. The structure of chitin was solved by Albert Hofmann in 1929, chitin is a modified polysaccharide that contains nitrogen, it is synthesized from units of N-acetyl-D-glucosamine. Therefore, chitin may be described as cellulose with one group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength, in its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. Combined with calcium carbonate, as in the shells of crustaceans and molluscs and this composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the body wall of a caterpillar to the stiff. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry, scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, the multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes. Chitosan is produced commercially by deacetylation of chitin, chitosan is soluble in water, chitin producing organisms like protozoa, fungi, arthropods, and nematodes are often pathogens in other species. Keratinocytes in skin can also react to chitin or chitin fragments, according to in vitro studies, chitin is sensed by receptors, such as FIBCD1, KLRB1, REG3G, Toll-like receptor 2, CLEC7A, and mannose receptors. Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1, the first chitin receptor was cloned in 2006. When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, commensal fungi that have ways to interact with the host immune response that as of 2016 were not well understood. Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors, zymoseptoria tritici is an example of a fungal pathogen that has such blocking proteins, it is a major pest in wheat crops. Chitin was probably present in the exoskeletons of Cambrian arthropods such as trilobites, the oldest preserved chitin dates to the Oligocene, about 25 million years ago, consisting of a scorpion encased in amber
13.
Macromolecule
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A macromolecule is a very large molecule, such as protein, commonly created by polymerization of smaller subunits. They are typically composed of thousands of atoms or more, the most common macromolecules in biochemistry are biopolymers and large non-polymeric molecules. Synthetic macromolecules include common plastics and synthetic fibres as well as materials such as carbon nanotubes. The term macromolecule was coined by Nobel laureate Hermann Staudinger in the 1920s, usage of the term to describe large molecules varies among the disciplines. According to the standard IUPAC definition, the term macromolecule as used in science refers only to a single molecule. For example, a polymeric molecule is appropriately described as a macromolecule or polymer molecule rather than a polymer. Because of their size, macromolecules are not conveniently described in terms of stoichiometry alone, the structure of simple macromolecules, such as homopolymers, may be described in terms of the individual monomer subunit and total molecular mass. Complicated biomacromolecules, on the hand, require multi-faceted structural description such as the hierarchy of structures used to describe proteins. In British English. Macromolecules often have physical properties that do not occur for smaller molecules. For example, DNA in a solution can be simply by sucking the solution through an ordinary straw because the physical forces on the molecule can overcome the strength of its covalent bonds. The 1964 edition of Linus Paulings College Chemistry asserted that DNA in nature is never longer than about 5,000 base pairs and this error arose because biochemists were inadvertently breaking their samples into fragments. In fact, the DNA of chromosomes can be hundreds of millions of base pairs long, another common macromolecular property that does not characterize smaller molecules is their relative insolubility in water and similar solvents, instead forming colloids. Many require salts or particular ions to dissolve in water, similarly, many proteins will denature if the solute concentration of their solution is too high or too low. High concentrations of macromolecules in a solution can alter the rates and equilibrium constants of the reactions of other macromolecules and this comes from macromolecules excluding other molecules from a large part of the volume of the solution, thereby increasing the effective concentrations of these molecules. All living organisms are dependent on three essential biopolymers for their functions, DNA, RNA and Proteins. Each of these molecules is required for life since each plays a distinct, the simple summary is that DNA makes RNA, and then RNA makes proteins. DNA, RNA and proteins all consist of a structure of related building blocks. In general, they are all unbranched polymers, and so can be represented in the form of a string
14.
Amorphous solid
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In condensed matter physics and materials science, an amorphous or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. In some older books, the term has been used synonymously with glass, nowadays, glassy solid or amorphous solid is considered to be the overarching concept, and glass the more special case, A glass is an amorphous solid that exhibits a glass transition. Other types of solids include gels, thin films. Amorphous materials have a structure made of interconnected structural blocks. Even amorphous materials have some shortrange order at the length scale due to the nature of chemical bonding. Furthermore, in small crystals a large fraction of the atoms are the crystal, relaxation of the surface and interfacial effects distort the atomic positions. Amorphous phases are important constituents of thin films, which are layers of a few nm to some tens of µm thickness deposited upon a substrate. For higher values, the diffusion of deposited atomic species would allow for the formation of crystallites with long range atomic order. Regarding their applications, amorphous metallic layers played an important role in the discussion of a suspected superconductivity in amorphous metals, today, optical coatings made from TiO2, SiO2, Ta2O5 etc. and combinations of them in most cases consist of amorphous phases of these compounds. Much research is carried out into thin films as a gas separating membrane layer. Also, hydrogenated amorphous silicon, a-Si, H in short, is of significance for thin film solar cells. In case of a-Si, H the missing long-range order between silicon atoms is partly induced by the presence by hydrogen in the percent range, the occurrence of amorphous phases turned out as a phenomenon of particular interest for studying thin film growth. Remarkably, the growth of polycrystalline films is used and preceded by an initial amorphous layer. The most investigated example is represented by thin multicrystalline silicon films, an initial amorphous layer was observed in many studies. The phenomenon has been interpreted in the framework of Ostwalds rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. Experimental studies of the phenomenon require a clearly defined state of the substrate surface, the Physics of Structurally Disordered Matter, An Introduction. Amorphous Solids and the Liquid State
15.
Solubility
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Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
16.
Fructose
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Fructose, or fruit sugar, is a simple ketonic monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion, fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847. The name fructose was coined in 1857 by the English chemist William Miller, pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars. Fructose is found in honey, tree and vine fruits, flowers, berries, commercially, fructose is frequently derived from sugar cane, sugar beets, and corn. Crystalline fructose is the monosaccharide, dried, ground, and of high purity, high-fructose corn syrup is a mixture of glucose and fructose as monosaccharides. Sucrose is a compound with one molecule of glucose covalently linked to one molecule of fructose, all forms of fructose, including fruits and juices, are commonly added to foods and drinks for palatability and taste enhancement, and for browning of some foods, such as baked goods. About 240,000 tonnes of crystalline fructose are produced annually, leads to adverse health outcomes independent of any effects related to its presence as a component of total and free sugars. Crystalline fructose adopts a cyclic six-membered structure owing to the stability of its hemiketal and internal hydrogen-bonding and this form is formally called D-fructopyranose. In solution, fructose exists as a mixture of 70% fructopyranose and about 22% fructofuranose. Fructose may be fermented by yeast or bacteria. Yeast enzymes convert sugar to ethanol and carbon dioxide, the carbon dioxide released during fermentation will remain dissolved in water, where it will reach equilibrium with carbonic acid, unless the fermentation chamber is left open to the air. The dissolved carbon dioxide and carbonic acid produce the carbonation in bottled fermented beverages, fructose undergoes the Maillard reaction, non-enzymatic browning, with amino acids. Because fructose exists to an extent in the open-chain form than does glucose. Fructose readily dehydrates to give hydroxymethylfurfural and this process, in the future, may become part of a low-cost, carbon-neutral system to produce replacements for petrol and diesel from plants. The primary reason that fructose is used commercially in foods and beverages, besides its low cost, is its high relative sweetness and it is the sweetest of all naturally occurring carbohydrates. The relative sweetness of fructose has been reported in the range of 1. 2–1.8 times that of sucrose, however, it is the 6-membered ring form of fructose that is sweeter, the 5-membered ring form tastes about the same as usual table sugar. Warming fructose leads to formation of the 5-membered ring form, therefore, the relative sweetness decreases with increasing temperature. The sweetness of fructose is perceived earlier than that of sucrose or glucose, fructose can also enhance other flavors in the system
17.
Glyceraldehyde
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Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. It is the simplest of all common aldoses and it is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes from combining glycerol and aldehyde, as glyceraldehyde is glycerol with one hydroxymethyl group oxidized to an aldehyde, the stereochemical configuration can only be determined from the chemical structure, whereas the optical rotation can only be determined empirically. It was by a lucky guess that the molecular d- geometry was assigned to -glyceraldehyde in the late 19th century, in the d/l system, glyceraldehyde is used as the configurational standard for carbohydrates. Monosaccharides with an absolute configuration identical to -glyceraldehyde at the last stereocentre and those similar to -glyceraldehyde are assigned an l-. Glyceraldehyde can be prepared, along with dihydroxyacetone, by the oxidation of glycerol, for example with hydrogen peroxide. Dihydroxyacetone, the simplest ketose, is an isomer of glyceraldehyde, the enzyme glycerol dehydrogenase has two substrates, glycerol and NADP+, and 3 products, D-glyceraldehyde, NADPH and H+. The interconversion of the phosphates of glyceraldehyde and dihydroxyacetone, catalyzed by the enzyme triosephosphate isomerase, is an important intermediate step in glycolysis
18.
Function (biology)
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A biological function is the reason some object or process occurred in a system that evolved through a process of natural selection. In physiology, a function is an activity or process carried out by a system in an organism and this concept of function as opposed to form was central in biological explanations in classical antiquity, and in more modern times formed part of the Cuvier–Geoffroy debate. A functional characteristic is known in biology as an adaptation. From the point of view of natural selection, biological functions exist to contribute to fitness, for example, the function of chlorophyll in a plant is to capture the energy of sunlight for photosynthesis, which contributes to evolutionary success. Function is not the same as purpose in the teleological sense, in the philosophy of biology, evolution is a blind process which has no goal for the future. For example, a tree does not grow flowers for any purpose, to say a tree grows flowers to attract pollinators would be incorrect if the to implies purpose. A function describes what something does, not what its purpose is, however, teleological language is often used by biologists as a shorthand way of describing function, even though its applicability is disputed. The ethologist Niko Tinbergen named four questions, based on Aristotles Four Causes, 1) Mechanism, What mechanisms cause the animal to behave as it does. 2) Ontogeny, What developmental mechanisms in the animals embryology created the structures that cause the behaviour, 3) Function/adaptation, What is the evolutionary function of the behaviour. 4) Evolution, What is the phylogeny of the behaviour, or in other words, the questions are interdependent, so that, for example, adaptive function is constrained by embryonic development
19.
Cell wall
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A cell wall is a structural layer surrounding some types of cells, situated outside the cell membrane. It can be tough, flexible, and sometimes rigid and it provides the cell with both structural support and protection, and also acts as a filtering mechanism. Cell walls are present in most prokaryotes, in algae, plants and fungi, a major function is to act as pressure vessels, preventing over-expansion of the cell when water enters. The composition of cell walls varies between species and may depend on type and developmental stage. The primary cell wall of plants is composed of the polysaccharides cellulose, hemicellulose. Often, other such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess walls made of glycoproteins and polysaccharides such as carrageenan, in bacteria, the cell wall is composed of peptidoglycan. The cell walls of archaea have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, Fungi possess cell walls made of the glucosamine polymer chitin. Unusually, diatoms have a wall composed of biogenic silica. A plant cell wall was first observed and named by Robert Hooke in 1665, in 1804, Karl Rudolphi and J. H. F. Link proved that cells had independent cell walls, before, it had been thought that cells shared walls and that fluid passed between them this way. The mode of formation of the wall was controversial in the 19th century. Hugo von Mohl advocated the idea that the wall grows by apposition. Carl Nägeli believed that the growth of the wall in thickness, each theory was improved in the following decades, the apposition theory by Eduard Strasburger, and the intussusception theory by Julius Wiesner. In 1930, Ernst Münch coined the term apoplast in order to separate the living symplast from the dead plant region, Cell walls serve similar purposes in those organisms that possess them. They may give cells rigidity and strength, offering protection against mechanical stress, in multicellular organisms, they permit the organism to build and hold a definite shape. Cell walls also limit the entry of large molecules that may be toxic to the cell and they further permit the creation of stable osmotic environments by preventing osmotic lysis and helping to retain water. Their composition, properties, and form may change during the cell cycle, in most cells, the cell wall is flexible, meaning that it will bend rather than holding a fixed shape, but has considerable tensile strength
20.
Organic compound
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An organic compound is virtually any chemical compound that contains carbon, although a consensus definition remains elusive and likely arbitrary. Organic compounds are rare terrestrially, but of importance because all known life is based on organic compounds. The most basic petrochemicals are considered the building blocks of organic chemistry, for historical reasons discussed below, a few types of carbon-containing compounds, such as carbides, carbonates, simple oxides of carbon, and cyanides are considered inorganic. The distinction between organic and inorganic compounds, while useful in organizing the vast subject of chemistry. Organic chemistry is the science concerned with all aspects of organic compounds, Organic synthesis is the methodology of their preparation. The word organic is historical, dating to the 1st century, for many centuries, Western alchemists believed in vitalism. This is the theory that certain compounds could be synthesized only from their classical elements—earth, water, air, vitalism taught that these organic compounds were fundamentally different from the inorganic compounds that could be obtained from the elements by chemical manipulation. Vitalism survived for a while even after the rise of modern atomic theory and it first came under question in 1824, when Friedrich Wöhler synthesized oxalic acid, a compound known to occur only in living organisms, from cyanogen. A more decisive experiment was Wöhlers 1828 synthesis of urea from the inorganic salts potassium cyanate, urea had long been considered an organic compound, as it was known to occur only in the urine of living organisms. Wöhlers experiments were followed by others, in which increasingly complex organic substances were produced from inorganic ones without the involvement of any living organism. Even though vitalism has been discredited, scientific nomenclature retains the distinction between organic and inorganic compounds, still, even the broadest definition requires excluding alloys that contain carbon, including steel. The C-H definition excludes compounds that are considered organic, neither urea nor oxalic acid is organic by this definition, yet they were two key compounds in the vitalism debate. The IUPAC Blue Book on organic nomenclature specifically mentions urea and oxalic acid, other compounds lacking C-H bonds but traditionally considered organic include benzenehexol, mesoxalic acid, and carbon tetrachloride. Mellitic acid, which contains no C-H bonds, is considered an organic substance in Martian soil. The C-H bond-only rule also leads to somewhat arbitrary divisions in sets of carbon-fluorine compounds, for example, CF4 would be considered by this rule to be inorganic, whereas CF3H would be organic. Organic compounds may be classified in a variety of ways, one major distinction is between natural and synthetic compounds. Another distinction, based on the size of organic compounds, distinguishes between small molecules and polymers, natural compounds refer to those that are produced by plants or animals. Many of these are extracted from natural sources because they would be more expensive to produce artificially
21.
Viscose
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Viscose is both a semi-synthetic fiber, formerly called viscose rayon, or rayon and a solution of cellulose xanthate. The latter is produced by treating dissolving pulp with aqueous sodium hydroxide, byproducts of the production process include sodium thiocarbonate, sodium carbonate, and sodium sulfide. Viscose rayon fiber is a soft fiber commonly used in dresses, linings, shirts, shorts, coats, jackets and it is also used in industrial yarns, upholstery and carpets, and in the casting of Cellophane. When Viscose is made, the cellulose is made of wood pulp, Viscose rayon is a fiber of regenerated cellulose, it is structurally similar to cotton but may be produced from a variety of plants such as soy, bamboo, and sugar cane. Cellulose is a polymer of β-D-glucose units with the empirical formula n. To prepare viscose, dissolving pulp is treated with sodium hydroxide to form alkali cellulose. The alkali cellulose is then treated with carbon disulfide to form sodium cellulose xanthate, N + nCS2 → n The higher the ratio of cellulose to combined sulfur, the lower the solubility of the cellulose xanthate. The xanthate is dissolved in aqueous sodium hydroxide and allowed to depolymerize to a desired extent, the rate of depolymerization depends on temperature and is affected by the presence of various inorganic and organic additives, such as metal oxides and hydroxides. Air also affects the process since oxygen causes depolymerization. Rayon fiber is produced from the solutions by treatment with a mineral acid. The thread made from the cellulose is washed to remove residual acid. The sulfur is removed by the addition of sodium sulfide solution. The use of viscose is declining, in part because of the costs of its production. Carbon disulphide is a neurotoxic to humans, instead, rayon may be manufactured using the Lyocell process, which uses N-Methylmorpholine N-oxide as the solvent and produces little waste product, making it relatively eco-friendly. French scientist and industrialist Hilaire de Chardonnet — who invented the first artificial textile fiber, British scientists Charles Frederick Cross and Edward John Bevan took out British patent no. 8,700, Improvements in Dissolving Cellulose and Allied Compounds in May,1892, in 1893 they formed the Viscose Syndicate to grant licences, and in 1896 formed the British Viscoid Co. Ltd. to exploit the process. Art silk Cellophane Rayon Sausage casings Synthetic velvet Viscose, archived from the original on 2008-06-25
22.
Nitrogen
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Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772, although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. Nitrogen is the lightest member of group 15 of the periodic table, the name comes from the Greek πνίγειν to choke, directly referencing nitrogens asphyxiating properties. It is an element in the universe, estimated at about seventh in total abundance in the Milky Way. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2, dinitrogen forms about 78% of Earths atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids, in the nucleic acids, the human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, many industrially important compounds, such as ammonia, nitric acid, organic nitrates, and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen, the second strongest bond in any diatomic molecule. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric, Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many notable nitrogen-containing drugs, such as the caffeine and morphine or the synthetic amphetamines. Nitrogen compounds have a long history, ammonium chloride having been known to Herodotus. They were well known by the Middle Ages, alchemists knew nitric acid as aqua fortis, as well as other nitrogen compounds such as ammonium salts and nitrate salts. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold, the discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it noxious air. Though he did not recognise it as a different chemical substance, he clearly distinguished it from Joseph Blacks fixed air. The fact that there was a component of air that does not support combustion was clear to Rutherford, Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as air or azote, from the Greek word άζωτικός. In an atmosphere of nitrogen, animals died and flames were extinguished
23.
Arthropod
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An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs
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Exoskeleton
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An exoskeleton is the external skeleton that supports and protects an animals body, in contrast to the internal skeleton of, for example, a human. In usage, some of the kinds of exoskeletons are known as shells. Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, the shells of certain sponges and the various groups of shelled molluscs, including those of snails, clams, tusk shells, chitons and nautilus, are also exoskeletons. Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton, exoskeletons have a role in defense from pests and predators, support, and in providing an attachment framework for musculature. Exoskeletons contain chitin, the addition of calcium carbonate makes them harder and stronger, ingrowths of the arthropod exoskeleton known as apodemes serve as attachment sites for muscles. These structures are composed of chitin, and are six times as strong. Similar to tendons, apodemes can stretch to store energy for jumping. Many different species produce exoskeletons, which are composed of a range of materials, bone, cartilage, or dentine is used in the Ostracoderm fish and turtles. Chitin forms the exoskeleton in arthropods including insects, arachnids such as spiders, crustaceans such as crabs and lobsters, calcium carbonates constitute the shells of molluscs, brachiopods, and some tube-building polychaete worms. Silica forms the exoskeleton in the microscopic diatoms and radiolaria, one species of mollusc, the scaly-foot gastropod, even makes use of the iron sulfides greigite and pyrite. Some organisms, such as some foraminifera, agglutinate exoskeletons by sticking grains of sand, contrary to a common misconception, echinoderms do not possess an exoskeleton, as their test is always contained within a layer of living tissue. Exoskeletons have evolved many times,18 lineages evolved calcified exoskeletons alone. Further, other lineages have produced tough outer coatings analogous to an exoskeleton and this coating is constructed from bone in the armadillo, and hair in the pangolin. The armor of reptiles like turtles and Ankylosaurs is constructed of bone, crocodiles have bony scutes, since exoskeletons are rigid, they present some limits to growth. Organisms with open shells can grow by adding new material to the aperture of their shell, as is the case in snails, bivalves, a true exoskeleton, like that found in arthropods, must be shed when it is outgrown. A new exoskeleton is produced beneath the old one, as the old one is shed, the new skeleton is soft and pliable. The animal will pump itself up to expand the new shell to maximal size, when the shell has set, the empty space inside the new skeleton can be filled up as the animal eats. Failure to shed the exoskeleton once outgrown can result in the animal being suffocated within its own shell and this is the mechanism behind some insect pesticides, such as Azadirachtin
25.
Fungus
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A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from the other eukaryotic life kingdoms of plants, a characteristic that places fungi in a different kingdom from plants, bacteria and some protists, is chitin in their cell walls. Similar to animals, fungi are heterotrophs, they acquire their food by absorbing dissolved molecules, growth is their means of mobility, except for spores, which may travel through the air or water. Fungi are the principal decomposers in ecological systems and this fungal group is distinct from the structurally similar myxomycetes and oomycetes. The discipline of biology devoted to the study of fungi is known as mycology, in the past, mycology was regarded as a branch of botany, although it is now known fungi are genetically more closely related to animals than to plants. Abundant worldwide, most fungi are inconspicuous because of the size of their structures. Fungi include symbionts of plants, animals, or other fungi and they may become noticeable when fruiting, either as mushrooms or as molds. Fungi perform a role in the decomposition of organic matter and have fundamental roles in nutrient cycling. Since the 1940s, fungi have been used for the production of antibiotics, Fungi are also used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, the fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies. Fungi can break down manufactured materials and buildings, and become significant pathogens of humans, losses of crops due to fungal diseases or food spoilage can have a large impact on human food supplies and local economies. The fungus kingdom encompasses a diversity of taxa with varied ecologies, life cycle strategies. However, little is known of the biodiversity of Kingdom Fungi. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace, a group of all the fungi present in a particular area or geographic region is known as mycobiota, e. g. the mycobiota of Ireland. Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies. The fungi are now considered a kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago. Fungi have membrane-bound cytoplasmic organelles such as mitochondria, sterol-containing membranes and they have a characteristic range of soluble carbohydrates and storage compounds, including sugar alcohols, disaccharides, and polysaccharides
26.
Surgical thread
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Surgical suture is a medical device used to hold body tissues together after an injury or surgery. Application generally involves using a needle with a length of thread. A number of different shapes, sizes, and thread materials have been developed over its millennia of history, surgeons, physicians, dentists, podiatrists, eye doctors, registered nurses and other trained nursing personnel, medics, and clinical pharmacists typically engage in suturing. Surgical knots are used to secure the sutures, eyed or reusable needles are needles with holes called eyes which are supplied separate from their suture thread. The suture must be threaded on site, as is done when sewing at home, the advantage of this is that any thread and needle combination is possible to suit the job at hand. Swaged, or atraumatic, needles with sutures comprise a pre-packed eyeless needle attached to a length of suture thread. The suture manufacturer swages the suture thread to the eyeless atraumatic needle at the factory, the chief advantage of this is that the doctor or the nurse does not have to spend time threading the suture on the needle, which may be difficult for very fine needles and sutures. Also, the end of a swaged needle is narrower than the needle body. In eyed needles, the thread protrudes from the body on both sides, and at best causes drag. When passing through tissues, the eye needle and suture combination may thus traumatise tissues more than a swaged needle. There are several shapes of surgical needles and these include, Straight 1/4 circle 3/8 circle 1/2 circle. Subtypes of this shape include, from larger to smaller size, CT, CT-1, CT-2. These pop-offs are commonly used for interrupted sutures, where each suture is only passed once, sutures can withstand different amounts of force based on their size, this is quantified by the U. S. P. Suture thread is made from numerous materials, the original sutures were made from biological materials, such as catgut suture and silk. Most modern sutures are synthetic, including the absorbables polyglycolic acid, polylactic acid, Monocryl and polydioxanone as well as the non-absorbables nylon, polyester, PVDF, the FDA first approved triclosan-coated sutures in 2002, they have been shown to reduce the chances of wound infection. Sutures come in specific sizes and may be either absorbable or non-absorbable. Sutures must be enough to hold tissue securely but flexible enough to be knotted. They must be hypoallergenic and avoid the effect that would allow fluids
27.
Laminarin
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The molecule laminarin is a storage glucan found in brown algae. It is used as a food reserve in the same way that chrysolaminarin is used by phytoplankton. It is created by photosynthesis and is made up of β-glucan with β-branches and it is a linear polysaccharide, with a β, β ratio of 3,1. Its hydrolysis is catalyzed by enzymes such as laminarinase that breaks the β bonds
28.
Chrysolaminarin
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Chrysolaminarin is a linear polymer of β and β linked glucose units in a ratio of 11,1. It used to be known as leucosin, chrysolaminarin is alongside cellulose arguably one of the most common biopolymers in the world. Chrysolaminarin is a storage polysaccharide typically found in photosynthetic heterokonts and it is used as a carbohydrate food reserve by phytoplankton such as Bacillariophyta. Chrysolaminarin is stored inside the cells of these organisms dissolved in water, in addition, heterokont algae use oil as a storage compound. Besides energy reserve, oil helps the algae to control their buoyancy
29.
Xylan
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Xylan is a group of hemicelluloses that are found in plant cell walls and some algae. Xylans are polysaccharides made from units of xylose, xylans are almost as ubiquitous as cellulose in plant cell walls and contain predominantly β-D-xylose units linked as in cellulose. Typically the content of xylans in hardwoods are 10 -35 % of the hemicelluloses, the main xylan component in hardwoods is O-acetyl-4-O-methylglucuronoxylan and in softwoods the main xylan components are arabino-4-O-methylglucuronoxylans. In general softwood xylans differ from hardwood xylans by the lack of acetyl groups, some macrophytic green algae contain xylan especially those within the Codium and Bryopsis genera where it replaces cellulose in the cell wall matrix. Similarly, it replaces the inner fibrillar cell-wall layer of cellulose in some red algae, xylan is one of the foremost anti-nutritional factors in common use feedstuff raw materials. Xylooligosaccharides produced from xylan are considered as food or dietary fibers. New enzymes from yeast are discovered which exclusively converts xylan into only xylooligosaccharides-DP-3 to 7
30.
Galactomannan
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Galactomannans are polysaccharides consisting of a mannose backbone with galactose side groups. Guar gum has been used to add viscosity to artificial tears, galactomannans are used in foods as stabilisers. Guar and locust bean gum are used in ice cream to improve texture. LBG is also used extensively in cream cheese, fruit preparations, tara gum is seeing growing acceptability as a food ingredient but is still used to a much lesser extent than guar or LBG. Guar has the highest usage in foods, largely due to its low, galactomannan is a component of the cell wall of the mold Aspergillus and is released during growth. Detection of galactomannan in blood is used to diagnose invasive aspergillosis infections in humans and this is performed with monoclonal antibodies in a double-sandwich ELISA, this assay from Bio-Rad Laboratories was approved by the FDA in 2003 and is of moderate accuracy. The assay is most useful in patients who have had hemopoetic cell transplants
31.
Ruminant
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Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process typically requires the fermented ingesta to be regurgitated and chewed again, the process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word ruminant comes from the Latin ruminare, which means to chew over again, the roughly 150 species of ruminants includes both domestic and wild species. Ruminating mammals include cattle, goats, sheep, giraffes, yaks, deer, antelope and it has also been suggested that notoungulates also relied on rumination, as opposed to other antlantogenates that relied on the more typical hindgut fermentation, though this is not entirely certain. Taxonomically, the suborder Ruminantia is a lineage of herbivorous artiodactyls that includes the most advanced, the term ruminant is not synonymous with Ruminantia. The suborder Ruminantia includes many ruminant species, but does not include tylopods, the primary difference between a ruminant and nonruminant is that ruminants have a four-compartment stomach. The four parts are the rumen, reticulum, omasum, in the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud or bolus, the cud is then regurgitated and chewed to completely mix it with saliva and to break down the particle size. Fiber, especially cellulose and hemicellulose, is broken down in these chambers by microbes into the three volatile fatty acids, acetic acid, propionic acid, and butyric acid. Protein and nonstructural carbohydrate are also fermented, though the rumen and reticulum have different names, they represent the same functional space as digesta can move back and forth between them. Together, these chambers are called the reticulorumen, after this, the digesta is moved to the true stomach, the abomasum. The abomasum is the equivalent of the monogastric stomach. Digesta is finally moved into the intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulorumen are also digested in the small intestine, fermentation continues in the large intestine in the same way as in the reticulorumen. Only small amounts of glucose are absorbed from dietary carbohydrates, most dietary carbohydrates are fermented into VFAs in the rumen. The VFA propionate is used for around 70% of the glucose and glycogen produced, also, some mammals are pseudoruminants, which have a three-compartment stomach instead of four like ruminants. Pseudoruminants, like traditional ruminants, are foregut fermentors and most ruminate or chew cud, however, their anatomy and method of digestion differs significantly from that of a four-chambered ruminant. Monogastric herbivores, such as rhinoceroses, horses, and rabbits, are not ruminants and these hindgut fermenters digest cellulose in an enlarged cecum through the reingestion of the cecotrope
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Termite
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Termites are eusocial insects that are classified at the taxonomic rank of infraorder Isoptera, or as epifamily Termitoidae within the cockroach order Blattodea. Termites were once classified in an order from cockroaches. However, the first termites emerged during the Permian or even the Carboniferous. About 3,106 species are described, with a few hundred more left to be described. Although these insects are called white ants, they are not ants. Like ants and some bees and wasps from the separate order Hymenoptera, all colonies have fertile males called kings and one or more fertile females called queens. Termites mostly feed on plant material and cellulose, generally in the form of wood, leaf litter, soil. Termites are major detritivores, particularly in the subtropical and tropical regions, Termites are among the most successful groups of insects on Earth, colonising most landmasses except for Antarctica. Their colonies range in size from a few hundred individuals to enormous societies with several million individuals, Termite queens have the longest lifespan of any insect in the world, with some queens reportedly living up to 30 to 50 years. Unlike ants, which undergo a metamorphosis, each individual termite goes through an incomplete metamorphosis that proceeds through egg, nymph. Colonies are described as superorganisms because the termites form part of a self-regulating entity, Termites are a delicacy in the diet of some human cultures and are used in many traditional medicines. Several hundred species are significant as pests that can cause serious damage to buildings, crops. Some species, such as the West Indian drywood termite, are regarded as invasive species, the infraorder name Isoptera is derived from the Greek words iso and ptera, which refers to the nearly equal size of the fore and hind wings. Termite derives from the Latin and Late Latin word termes, altered by the influence of Latin terere from the earlier word tarmes, Termite nests were commonly known as terminarium or termitaria. In early English, termites were known as wood ants or white ants, the modern term was first used in 1781. DNA analysis from 16S rRNA sequences has supported a hypothesis, originally suggested by Cleveland and colleagues in 1934 and this earlier conclusion had been based on the similarity of the symbiotic gut flagellates in the wood-eating cockroaches to those in certain species of termites regarded as living fossils. In the 1960s additional evidence supporting that hypothesis emerged when F. A. McKittrick noted similar morphological characteristics between some termites and Cryptocercus nymphs. These similarities have led some authors to propose that termites be reclassified as a family, the Termitidae, within the order Blattodea
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Dietary fiber
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Dietary fiber or roughage is the indigestible portion of food derived from plants. It has two components, Soluble fiber, which dissolves in water, is readily fermented in the colon into gases and physiologically active byproducts. It delays gastric emptying which in turn can cause a feeling of fullness. Insoluble fiber, which does not dissolve in water, is inert and provides bulking, or it can be prebiotic. Bulking fibers absorb water as they move through the digestive system, Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed. Some types of soluble fiber absorb water to become a gelatinous, viscous substance which is fermented by bacteria in the digestive tract, some types of insoluble fiber have bulking action and are not fermented. Lignin, a major dietary insoluble fiber source, may alter the rate, other types of insoluble fiber, notably resistant starch, are fully fermented. A novel position has been adopted by the US Department of Agriculture to include functional fibers as isolated fiber sources that may be included in the diet, the term fiber is something of a misnomer, since many types of so-called dietary fiber are not actually fibrous. Food sources of fiber are often divided according to whether they provide soluble or insoluble fiber. Plant foods contain both types of fiber in varying degrees, according to the plants characteristics, a disadvantage of a diet high in fiber is the potential for significant intestinal gas production and bloating. Originally, fiber was defined to be the components of plants that resist human digestive enzymes, the definition was later changed to also include resistant starch, along with inulin and other oligosaccharides. Official definition of dietary fiber differs a little among different institutions, Dietary fibers are found in fruits, vegetables, the exact amount of fiber contained in the food can be seen in the following table of expected fiber in USDA food groups/subgroups Dietary fiber is found in plants. While all plants contain some fiber, plants with high concentrations are generally the most practical source. Fiber-rich plants can be eaten directly, or, alternatively, they can be used to make supplements and fiber-rich processed foods. The Academy of Nutrition and Dietetics, formerly the American Dietetic Association, some plants contain significant amounts of soluble and insoluble fiber. For example, plums and prunes have a thick skin covering a juicy pulp, the skin is a source of insoluble fiber, whereas soluble fiber is in the pulp. Grapes also contain an amount of fiber. The root of the plant, or glucomannan, produces results similar to fiber
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Gastrointestinal tract
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Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines. A tract is a collection of related anatomic structures or a series of connected body organs, the mouth, oesophagus, stomach, and intestines are part of the human alimentary canal. All bilaterians have a gastrointestinal tract, also called a gut or an alimentary canal and this is a tube that transfers food to the organs of digestion. In large bilaterians, the gastrointestinal tract generally also has an exit, some small bilaterians have no anus and dispose of solid wastes by other means. The gastrointestinal tract contains thousands of different bacteria in their gut flora, the human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. In contrast, the digestive system comprises the gastrointestinal tract plus the accessory organs of digestion. The tract may also be divided into foregut, midgut, and hindgut, the whole human GI tract is about nine metres long at autopsy. The GI tract releases hormones from enzymes to help regulate the digestive process, the structure and function can be described both as gross anatomy and as microscopic anatomy or histology. The tract itself is divided into upper and lower tracts, the upper gastrointestinal tract consists of the buccal cavity, pharynx, esophagus, stomach, and duodenum. The exact demarcation between the upper and lower tracts is the muscle of the duodenum. Upon dissection, the duodenum may appear to be an organ, but it is divided into four segments based upon function, location. The four segments of the duodenum are as follows, bulb, descending, horizontal, the suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm. The suspensory muscle is an important anatomical landmark which shows the division between the duodenum and the jejunum, the first and second parts of the small intestine. This is a muscle which is derived from the embryonic mesoderm. The lower gastrointestinal tract includes most of the intestine and all of the large intestine. In humans, the intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum, colon, rectum. The small intestine begins at the duodenum, which receives food from the stomach and it is a tubular structure, usually between 6 and 7 m long. The area of the human, adult small intestinal mucosa is about 30 m2 and its main function is to absorb the products of digestion into the bloodstream
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Bile acids
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Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Different molecular forms of bile acids can be synthesized in the liver by different species, Bile acids are conjugated with taurine or glycine in the liver, forming primary bile acids. The sodium and potassium salts of bile acids are called bile salts, primary bile acids are those synthesized by the liver. Secondary bile acids result from actions in the colon. In humans, taurocholic acid and glycocholic acid and taurochenodeoxycholic acid, Bile acids compose about 80% of the organic compounds in bile. An increased secretion of bile acids produces an increase in bile flow and they also have hormonal actions throughout the body, particularly through the farnesoid X receptor and GPBAR1. Bile acid synthesis occurs in cells which synthesize primary bile acids via cytochrome P450-mediated oxidation of cholesterol in a multi-step process. Approximately 600 mg of bile salts are synthesized daily to replace bile acids lost in the feces, the rate-limiting step is the addition of a hydroxyl group on position 7 of the steroid nucleus by the enzyme cholesterol 7 alpha-hydroxylase. This enzyme is down-regulated by cholic acid, up-regulated by cholesterol and is inhibited by the actions of the ileal hormone FGF15/19. Prior to secreting any of the acids, liver cells conjugate them with one of two amino acids, glycine or taurine, to form a total of 8 possible conjugated bile acids. These conjugated bile acids are referred to as bile salts because of their physiologically-important acid-base properties. Conjugating bile acids with amino acids lowers the pKa of the conjugate to between 1 and 4. Cholic acid is converted into deoxycholic acid and chenodeoxycholic acid into lithocholic acid, all four of these bile acids can be taken back up into the blood stream, return to the liver, and be re-secreted in a process known as enterohepatic circulation. As amphipathic molecules with hydrophobic and hydrophilic regions, conjugated bile salts sit at the interface and, at the right concentration. The added solubility of conjugated bile salts aids in their function by preventing passive re-absorption in the small intestine, as a result, the concentration of bile acids/salts in the small intestine is high enough to form micelles and solubilize lipids. Critical micellar concentration refers to both a property of the bile acid itself and amount of bile acid necessary to function in the spontaneous. Bile acid-containing micelles aid lipases to digest lipids and bring them near the intestinal brush border membrane, synthesis of bile acids is a major route of cholesterol metabolism in most species other than humans. The body produces about 800 mg of cholesterol per day and about half of that is used for bile acid synthesis producing 400–600 mg daily, human adults secrete between 12-18 g of bile acids into the intestine each day, mostly after meals
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Cholesterol
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Cholesterol, from the Ancient Greek chole- and stereos followed by the chemical suffix -ol for an alcohol, is an organic molecule. Cholesterol enables animal cells to dispense with a wall, thereby allowing animal cells to change shape rapidly. In addition to its importance for cell structure, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid. Cholesterol is the principal sterol synthesized by all animals, in vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes, although there are exceptions, such as Mycoplasma. François Poulletier de la Salle first identified cholesterol in solid form in gallstones in 1769, however, it was not until 1815 that chemist Michel Eugène Chevreul named the compound cholesterine. Furthermore, it can be absorbed directly from animal-based foods, a human male weighing 68 kg normally synthesizes about 1 gram per day, and his body contains about 35 g, mostly contained within the cell membranes. Typical daily cholesterol dietary intake for a man in the United States is 307 mg, most ingested cholesterol is esterified, and esterified cholesterol is poorly absorbed. The body also compensates for any absorption of cholesterol by reducing cholesterol synthesis. For these reasons, cholesterol in food, seven to ten hours after ingestion, has little and it is also important to recognize, however, that the concentrations measured in the samples of blood plasma vary with the measurement methods used. Cholesterol is recycled in the body, the liver excretes it in a non-esterified form into the digestive tract. Typically, about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream, plants make cholesterol in very small amounts. Plants manufacture phytosterols, which can compete with cholesterol for reabsorption in the intestinal tract, when intestinal lining cells absorb phytosterols, in place of cholesterol, they usually excrete the phytosterol molecules back into the GI tract, an important protective mechanism. Cholesterol, given that it composes about 30% of all cell membranes, is required to build. The membrane remains stable and durable without being rigid, allowing cells to change shape. In this structural role, cholesterol also reduces the permeability of the membrane to neutral solutes, hydrogen ions. Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling, cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including caveola-dependent and clathrin-dependent endocytosis. The role of cholesterol in endocytosis of these types can be investigated by using methyl beta cyclodextrin to remove cholesterol from the plasma membrane, in multiple layers, cholesterol and phospholipids, both electrical insulators, can facilitate speed of transmission of electrical impulses along nerve tissue
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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
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Potato
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The potato is a starchy, tuberous crop from the perennial nightshade Solanum tuberosum. The word potato may refer either to the plant itself or to the edible tuber, in the Andes, where the species is indigenous, there are some other closely related cultivated potato species. Potatoes were introduced to Europe in the half of the 16th century by the Spanish. It is the worlds fourth-largest food crop, following maize, wheat, the green leaves and green skins of tubers exposed to the light are toxic. Wild potato species can be throughout the Americas from the United States to southern Chile. Following centuries of breeding, there are now over a thousand different types of potatoes. However, the importance of the potato is variable and changing rapidly. As of 2007 China led the world in production, and nearly a third of the worlds potatoes were harvested in China. The English word potato comes from Spanish patata, the Spanish Royal Academy says the Spanish word is a compound of the Taíno batata and the Quechua papa. The 16th-century English herbalist John Gerard used the terms bastard potatoes and Virginia potatoes for this species, potatoes are occasionally referred to as Irish potatoes or white potatoes in the United States, to distinguish them from sweet potatoes. The name spud for a small potato comes from the digging of soil prior to the planting of potatoes, the word spud traces back to the 16th century. It subsequently transferred over to a variety of digging tools, around 1845, the name transferred to the tuber itself. It was Mario Peis 1949 The Story of Language that can be blamed for the false origin. Pei writes, the potato, for its part, was in disrepute some centuries ago, some Englishmen who did not fancy potatoes formed a Society for the Prevention of Unwholesome Diet. The initials of the words in this title gave rise to spud. Like most other pre-20th century acronymic origins, this is false, Potato plants are herbaceous perennials that grow about 60 cm high, depending on variety, with the leaves dying back after flowering, fruiting and tuber formation. They bear white, pink, red, blue, or purple flowers with yellow stamens, in general, the tubers of varieties with white flowers have white skins, while those of varieties with colored flowers tend to have pinkish skins. Potatoes are mostly cross-pollinated by insects such as bumblebees, which carry pollen from other potato plants, tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties
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Rice
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Rice is the seed of the grass species Oryza sativa or Oryza glaberrima. As a cereal grain, it is the most widely consumed staple food for a part of the worlds human population. It is the agricultural commodity with the third-highest worldwide production, after sugarcane and maize, wild rice, from which the crop was developed, may have its native range in Australia. Chinese legends attribute the domestication of rice to Shennong, the emperor of China. Genetic evidence has shown that rice originates from a single domestication 8, previously, archaeological evidence had suggested that rice was domesticated in the Yangtze River valley region in China. From East Asia, rice was spread to Southeast and South Asia, Rice was introduced to Europe through Western Asia, and to the Americas through European colonization. There are many varieties of rice and culinary preferences tend to vary regionally, in some areas such as the Far East or Spain, there is a preference for softer and stickier varieties. Rice, a monocot, is grown as an annual plant, although in tropical areas it can survive as a perennial. The rice plant can grow to 1–1.8 m tall, occasionally more depending on the variety and it has long, slender leaves 50–100 cm long and 2–2.5 cm broad. The small wind-pollinated flowers are produced in a branched arching to pendulous inflorescence 30–50 cm long, the edible seed is a grain 5–12 mm long and 2–3 mm thick. Rice cultivation is well-suited to countries and regions with low costs and high rainfall, as it is labor-intensive to cultivate. However, rice can be grown practically anywhere, even on a hill or mountain area with the use of water-controlling terrace systems. Although its parent species are native to Asia and certain parts of Africa, centuries of trade, the traditional method for cultivating rice is flooding the fields while, or after, setting the young seedlings. The name wild rice is used for species of the genera Zizania and Porteresia. The Greek word is the source of all European words, the origin of the Greek word is unclear. It is sometimes held to be from the Tamil word அரிசி, however, Krishnamurti disagrees with the notion that Old Tamil arici is the source of the Greek term, and proposes that it was borrowed from descendants of Proto-Dravidian *wariñci instead. The varieties of rice are typically classified as long-, medium-, the grains of long-grain rice tend to remain intact after cooking, medium-grain rice becomes more sticky. Medium-grain rice is used for dishes, for risotto in Italy
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Wheat
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Wheat is a cereal grain, originally from the Levant region but now cultivated worldwide. In 2016, world production of wheat was 749 million tonnes, making it the second most-produced cereal after maize, since 1960, world production of wheat and other grain crops has tripled and is expected to grow further through the middle of the 21st Century. This grain is grown on land area than any other commercial food. World trade in wheat is greater than for all other crops combined, globally, wheat is the leading source of vegetal protein in human food, having a protein content of about 13%, which is relatively high compared to other major cereals and staple foods. The archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BCE. In a small part of the population, gluten – the major part of wheat protein – can trigger coeliac disease, non-coeliac gluten sensitivity, gluten ataxia. Cultivation and repeated harvesting and sowing of the grains of wild grasses led to the creation of domestic strains, in domesticated wheat, grains are larger, and the seeds remain attached to the ear by a toughened rachis during harvesting. In wild strains, a more fragile rachis allows the ear to easily shatter, as the traits that improve wheat as a food source also involve the loss of the plants natural seed dispersal mechanisms, highly domesticated strains of wheat cannot survive in the wild. Cultivation of wheat began to spread beyond the Fertile Crescent after about 8000 BCE, jared Diamond traces the spread of cultivated emmer wheat starting in the Fertile Crescent sometime before 8800 BCE. Archaeological analysis of wild emmer indicates that it was first cultivated in the southern Levant with finds dating back as far as 9600 BCE, Genetic analysis of wild einkorn wheat suggests that it was first grown in the Karacadag Mountains in southeastern Turkey. Dated archeological remains of wheat in settlement sites near this region, including those at Abu Hureyra in Syria. With the anomalous exception of two grains from Iraq ed-Dubb, the earliest carbon-14 date for einkorn wheat remains at Abu Hureyra is 7800 to 7500 years BCE. Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 and 8400 BCE, that is, in the Neolithic period and these remains were dated by Willem van Zeist and his assistant Johanna Bakker-Heeres to 8800 BCE. They also concluded that the settlers of Tell Aswad did not develop this form of emmer themselves, the cultivation of emmer reached Greece, Cyprus and India by 6500 BCE, Egypt shortly after 6000 BCE, and Germany and Spain by 5000 BCE. The early Egyptians were developers of bread and the use of the oven, by 3000 BCE, wheat had reached the British Isles and Scandinavia. A millennium later it reached China, the oldest evidence for hexaploid wheat has been confirmed through DNA analysis of wheat seeds, dating to around 6400-6200 BCE, recovered from Çatalhöyük. The first identifiable bread wheat with sufficient gluten for yeasted breads has been identified using DNA analysis in samples from a dating to approximately 1350 BCE at Assiros in Macedonia. From Asia, wheat continued to spread throughout Europe, in the British Isles, wheat straw was used for roofing in the Bronze Age, and was in common use until the late 19th century
