1.
Food energy
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Food energy is chemical energy that animals derive from food and molecular oxygen through the process of cellular respiration. Humans and other animals need a minimum intake of energy to sustain their metabolism. Foods are composed chiefly of carbohydrates, fats, proteins, alcohol, water, vitamins, carbohydrates, fats, proteins, alcohol, and water represent virtually all the weight of food, with vitamins and minerals making up only a small percentage of the weight. Organisms derive food energy from carbohydrates, fats and proteins as well as organic acids, polyols. Some diet components that provide little or no energy, such as water, minerals, vitamins, cholesterol. Water, minerals, vitamins, and cholesterol are not broken down, fiber, a type of carbohydrate, cannot be completely digested by the human body. Ruminants can extract energy from the respiration of cellulose because of bacteria in their rumens. Using the International System of Units, researchers measure energy in joules or in its multiples, the kilojoule is most often used for food-related quantities. An older metric system unit of energy, still used in food-related contexts, is the calorie, more precisely. Within the European Union, both the kilocalorie and kilojoule appear on nutrition labels, in many countries, only one of the units is displayed, in the US and Canada labels spell out the unit as calorie or as Calorie. Fats and ethanol have the greatest amount of energy per gram,37 and 29 kJ/g. Proteins and most carbohydrates have about 17 kJ/g, carbohydrates that are not easily absorbed, such as fiber, or lactose in lactose-intolerant individuals, contribute less food energy. Polyols and organic acids contribute 10 kJ/g and 13 kJ/g respectively, the amount of water, fat, and fiber in foods determines those foods energy density. Theoretically, one could measure food energy in different ways, using the Gibbs free energy of combustion, however, the convention is to use the heat of the oxidation reaction, with the water substance produced being in the liquid phase. The American chemist Wilbur Atwater worked these corrections out in the late 19th century, based on the work of Atwater, it became common practice to calculate energy content of foods using 4 kcal/g for carbohydrates and proteins and 9 kcal/g for lipids. The system was improved by Annabel Merrill and Bernice Watt of the USDA. Many governments require food manufacturers to label the energy content of their products, in the European Union, manufacturers of packaged food must label the nutritional energy of their products in both kilocalories and kilojoules, when required. In Australia and New Zealand, the energy must be stated in kilojoules
2.
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
3.
Fat
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Fat is one of the three main macronutrients, along with carbohydrate and protein. Fats, also known as triglycerides, are esters of three fatty acid chains and the alcohol glycerol, the terms oil, fat, and lipid are often confused. Oil normally refers to a fat with short or unsaturated fatty acid chains that is liquid at room temperature, lipid is the general term, as a lipid is not necessarily a triglyceride. Fats, like lipids, are generally hydrophobic, and are soluble in organic solvents. Fat is an important foodstuff for many forms of life, and they are a necessary part of the diet of most heterotrophs. Some fatty acids that are set free by the digestion of fats are called essential because they cannot be synthesized in the body from simpler constituents, there are two essential fatty acids in human nutrition, alpha-linolenic acid and linoleic acid. Other lipids needed by the body can be synthesized from these, fats and other lipids are broken down in the body by enzymes called lipases produced in the pancreas. Fats and oils are categorized according to the number and bonding of the atoms in the aliphatic chain. Fats that are saturated fats have no double bonds between the carbons in the chain, unsaturated fats have one or more double bonded carbons in the chain. The nomenclature is based on the end of the chain. This end is called the end or the n-end. Thus alpha-linolenic acid is called an omega-3 fatty acid because the 3rd carbon from that end is the first double bonded carbon in the counting from that end. Some oils and fats have double bonds and are therefore called polyunsaturated fats. Unsaturated fats can be divided into cis fats, which are the most common in nature, and trans fats. Unsaturated fats can be altered by reaction with hydrogen effected by a catalyst and this action, called hydrogenation, tends to break all the double bonds and makes a fully saturated fat. However, trans fats are generated during hydrogenation as contaminants created by a side reaction on the catalyst during partial hydrogenation. Saturated fats can stack themselves in a closely packed arrangement, so they can easily and are typically solid at room temperature. For example, animal fats tallow and lard are high in saturated fatty acid content and are solids, olive and linseed oils on the other hand are unsaturated and liquid
4.
Saturated fat
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A saturated fat is a type of fat in which the fatty acids all have single bonds. A fat is made of two kinds of molecules, monoglyceride and fatty acids. Fats are made of chains of carbon atoms. Some carbon atoms are linked by bonds and others are linked by double bonds. Double bonds can react with hydrogen to form single bonds and they are called saturated, because the second bond is broken up and each half of the bond is attached to a hydrogen atom. The fats of plants and fish are generally unsaturated, various fats contain different proportions of saturated and unsaturated fat. Certain vegetable products have high saturated fat content, such as coconut oil, many prepared foods are high in saturated fat content, such as pizza, dairy desserts, and sausage. The effect of saturated fat on risk of disease is controversial, many reviews recommend a diet low in saturated fat and argue it will lower risks of cardiovascular diseases, diabetes, or death. However, other reviews have rejected those arguments or advocated for examining the proportion of saturated to unsaturated fat in the diet, while nutrition labels regularly combine them, the saturated fatty acids appear in different proportions among food groups. Lauric and myristic acids are most commonly found in tropical oils, the saturated fat in meat, eggs, cacao, and nuts is primarily the triglycerides of palmitic and stearic acids. Sources of lower saturated fat but higher proportions of unsaturated fatty acids include olive oil, peanut oil, canola oil, avocados, safflower, corn, sunflower, soy, the effect of saturated fat on cardiovascular disease is controversial. Until the picture becomes clearer, experts recommend people stick to the current guidelines on fat consumption, the consumption of saturated fat is generally considered a risk factor for dyslipidemia, which in turn is a risk factor for some types of cardiovascular disease. There are strong, consistent, and graded relationships between saturated fat intake, blood levels, and the mass occurrence of cardiovascular disease. The relationships are accepted as causal, meta-analyses have found a significant relationship between saturated fat and serum cholesterol levels. High total cholesterol levels, which may be caused by many factors, are associated with a risk of cardiovascular disease. However, other indicators measuring cholesterol such as high total/HDL cholesterol ratio are more predictive than total serum cholesterol, in a study of myocardial infarction in 52 countries, the ApoB/ApoA1 ratio was the strongest predictor of CVD among all risk factors. Different saturated fatty acids have differing effects on various lipid levels, a meta-analysis published in 2003 found a significant positive relationship in both control and cohort studies between saturated fat and breast cancer. However two subsequent reviews have found weak or insignificant associations of saturated fat intake and breast cancer risk, one review found limited evidence for a positive relationship between consuming animal fat and incidence of colorectal cancer
5.
Monounsaturated fat
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In biochemistry and nutrition, monounsaturated fatty acids are fatty acids that have one double bond in the fatty acid chain with all of the remainder carbon atoms being single-bonded. By contrast, polyunsaturated fatty acids have more than one double bond, Fatty acids are long-chained molecules having an alkyl group at one end and a carboxylic acid group at the other end. Monounsaturated fatty acids are liquids at room temperature and semisolid or solid when refrigerated, common monounsaturated fatty acids are palmitoleic acid, cis-vaccenic acid and oleic acid. Palmitoleic acid has 16 carbon atoms with the first double bond occurring 7 carbon atoms away from the methyl group and it can be lengthened to the 18-carbon cis-vaccenic acid. Oleic acid has 18 carbon atoms with the first double bond occurring 9 carbon atoms away from the acid group. The illustrations below show a molecule of acid in Lewis formula. Polyunsaturated fats protect against cardiovascular disease by providing more membrane fluidity than monounsaturated fats, the large scale KANWU study found that increasing monounsaturated fat and decreasing saturated fat intake could improve insulin sensitivity, but only when the overall fat intake of the diet was low. However, some monounsaturated fatty acids may promote resistance, whereas polyunsaturated fatty acids may be protective against insulin resistance. Studies have shown that substituting dietary monounsaturated fat for saturated fat is associated with increased physical activity. More physical activity was associated with a higher-oleic acid diet than one of a palmitic acid diet, from the study, it is shown that more monounsaturated fats lead to less anger and irritability. Foods containing monounsaturated fats reduce low-density lipoprotein cholesterol, while possibly increasing high-density lipoprotein cholesterol, however, their true ability to raise HDL is still in debate. Levels of oleic along with other monounsaturated fatty acids in red cell membranes were positively associated with breast cancer risk. The saturation index of the same membranes was inversely associated with breast cancer risk, monounsaturated fats and low SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Both of these depend on the activity of the enzyme delta-9 desaturase. In children, consumption of monounsaturated oils is associated with healthier serum lipid profiles, the Mediterranean Diet is one heavily influenced by monounsaturated fats. The diet in Crete is fairly high in total fat yet affords a protection from coronary heart disease. Monounsaturated fats are found in foods such as red meat, whole milk products, nuts and high fat fruits such as olives. Olive oil is about 75% monounsaturated fat, the high oleic variety sunflower oil contains as much as 85% monounsaturated fat
6.
Polyunsaturated fat
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Polyunsaturated fats are lipids in which the constituent hydrocarbon chain possesses two or more carbon–carbon double bonds. Polyunsaturated fat can be mostly in nuts, seeds, fish, algae, leafy greens. Unsaturated refers to the fact that the molecules contain less than the amount of hydrogen. These materials exist as cis or trans isomers depending on the geometry of the double bond, saturated fats have hydrocarbon chains which can be most readily aligned. The hydrocarbon chains in trans fats align more readily than those in cis fats and this means that, in general, the melting points of fats increase from cis to trans unsaturated and then to saturated. See the section on chemical structure of fats for more information, the position of the carbon-carbon double bonds in carboxylic acid chains in fats is designated by Greek letters. The carbon atom closest to the group is the alpha carbon. In fatty acids the carbon atom of the group at the end of the hydrocarbon chain is called the omega carbon because omega is the last letter of the Greek alphabet. Omega-3 fatty acids have a double bond three carbons away from the carbon, whereas omega-6 fatty acids have a double bond six carbons away from the methyl carbon. The illustration below shows the omega-6 fatty acid, linoleic acid, while it is the nutritional aspects of polyunsaturated fats that are generally of greatest interest, these materials do also have non-food applications. Drying oils, which polymerize on exposure to oxygen to form films, are polyunsaturated fats. The most common ones are linseed oil, tung oil, poppy seed oil, perilla oil and these oils are used to make paints and varnishes. In preliminary research, omega-3 fatty acids in algal oil, fish oil, fish, ongoing research indicates that omega-6 fatty acids in sunflower oil and safflower oil may also reduce the risk of cardiovascular disease. Among n-3 fatty acids, neither long-chain nor short-chain forms were associated with breast cancer risk. High levels of acid, however, the most abundant n-3 PUFA in erythrocyte membranes, were associated with a reduced risk of breast cancer. The DHA obtained through the consumption of polyunsaturated fatty acids is associated with cognitive. In addition DHA is vital for the grey matter structure of the human brain, dietary intake of polyunsaturated fatty acids has been shown in preliminary studies to decrease the risk of developing amyotrophic lateral sclerosis. The importance of the ratio of essential fatty acids as established by comparative studies shows an Omega-6
7.
Protein (nutrient)
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Proteins are essential nutrients for the human body. They are one of the blocks of body tissue. As a fuel, proteins provide as much energy density as carbohydrates,4 kcal per gram, in contrast, the most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition. Proteins are polymer chains made of amino acids linked together by peptide bonds, during human digestion, proteins are broken down in the stomach to smaller polypeptide chains via hydrochloric acid and protease actions. This is crucial for the synthesis of the amino acids that cannot be biosynthesized by the body. There are nine amino acids which humans must obtain from their diet in order to prevent protein-energy malnutrition. They are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, there are five dispensable amino acids which humans are able to synthesize in the body. These five are alanine, aspartic acid, asparagine, glutamic acid and these six are arginine, cysteine, glycine, glutamine, proline and tyrosine. Humans need the essential amino acids in certain ratios, some protein sources contain amino acids in a more or less complete sense. This has given rise to various ranking systems for protein sources, Dietary sources of protein include both animals and plants, meats, dairy products, fish and eggs as well as grains, legumes and nuts. Vegetarians and vegans can get enough essential amino acids by eating a variety of plant proteins and it is commonly believed that athletes should consume a higher-than-normal protein intake to maintain optimal physical performance. Protein is a nutrient needed by the body for growth. Aside from water, proteins are the most abundant kind of molecules in the body, Protein can be found in all cells of the body and is the major structural component of all cells in the body, especially muscle. This also includes body organs, hair and skin, proteins are also used in membranes, such as glycoproteins. When broken down into amino acids, they are used as precursors to acid, co-enzymes, hormones, immune response, cellular repair. Additionally, protein is needed to form blood cells, proteins are believed to increase performance in terms of athletics. Amino acids, the blocks of proteins, are used for building muscle tissue. Protein is only used as fuel when carbohydrates are low
8.
Tryptophan
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Tryptophan is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, tryptophan is also a precursor to the neurotransmitters serotonin and melatonin. Like other amino acids, tryptophan is a zwitterion at physiological pH where the group is protonated. The isolation of tryptophan was first reported by Frederick Hopkins in 1901 through hydrolysis of casein, from 600 grams of crude casein one obtains 4-8 grams of tryptophan. As an essential amino acid, tryptophan is not synthesized from more basic substances in humans and other animals, the ring of the ribose moiety is opened and subjected to reductive decarboxylation, producing indole-3-glycerinephosphate, this, in turn, is transformed into indole. In the last step, tryptophan synthase catalyzes the formation of tryptophan from indole and these strains carry either mutations that prevent the reuptake of aromatic amino acids or multiple/overexpressed trp operons. The conversion is catalyzed by the tryptophan synthase. For many organisms, tryptophan is needed to prevent illness or death, amino acids, including tryptophan, act as building blocks in protein biosynthesis, and proteins are required to sustain life. In addition, tryptophan functions as a precursor for the following compounds, Serotonin. Serotonin, in turn, can be converted to melatonin, via N-acetyltransferase and 5-hydroxyindole-O-methyltransferase activities, niacin, also known as vitamin B3, is synthesized from tryptophan via kynurenine and quinolinic acids as key biosynthetic intermediates. The disorder fructose malabsorption causes improper absorption of tryptophan in the intestine, reduced levels of tryptophan in the blood, some studies did not find reduced tryptophan in cases of lactose maldigestion. In bacteria that synthesize tryptophan, high levels of this amino acid activate a repressor protein. Binding of this repressor to the tryptophan operon prevents transcription of downstream DNA that codes for the involved in the biosynthesis of tryptophan. So high levels of tryptophan prevent tryptophan synthesis through a feedback loop and. The genetic organisation of the trp operon thus permits tightly regulated, tryptophan is a routine constituent of most protein-based foods or dietary proteins. Contrary to the belief that turkey contains an abundance of tryptophan. A common assertion in the US is that consumption of turkey meat results in drowsiness
9.
Threonine
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Threonine encoded by the codons ACU, ACC, ACA, and ACG is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, threonine is synthesized from aspartate in bacteria such as E. coli. Threonine sidechains are often bonded, the commonest small motifs formed are ST turns, ST motifs. The threonine residue is susceptible to numerous posttranslational modifications, the hydroxyl side-chain can undergo O-linked glycosylation. In addition, threonine residues undergo phosphorylation through the action of a threonine kinase, in its phosphorylated form, it can be referred to as phosphothreonine. It is a precursor of glycine, and can be used as a prodrug to reliably elevate brain glycine levels, threonine was discovered as the last of the 20 common proteinogenic amino acids in 1935s by William Cumming Rose, collaborating with Curtis Meyer and William Rose. Threonine can exist in four possible stereoisomers with the following configurations, however, the name L-threonine is used for one single diastereomer, -2-amino-3-hydroxybutanoic acid. The second stereoisomer, which is present in nature, is called L-allo-threonine. The two stereoisomers - and -2-amino-3-hydroxybutanoic acid are only of minor importance, as an essential amino acid, threonine is not synthesized in humans, hence we must ingest threonine in the form of threonine-containing proteins. In plants and microorganisms, threonine is synthesized from aspartic acid via α-aspartyl-semialdehyde, homoserine undergoes O-phosphorylation, this phosphate ester undergoes hydrolysis concomitant with relocation of the OH group. Enzymes involved in a typical biosynthesis of threonine include, aspartokinase β-aspartate semialdehyde dehydrogenase homoserine dehydrogenase homoserine kinase threonine synthase, threonine is metabolized in two ways, It is converted to pyruvate via threonine dehydrogenase. An intermediate in this pathway can undergo thiolysis with CoA to produce acetyl-CoA, in humans, it is converted to α-ketobutyrate. This is the pathway for threonine degradation. The mechanism of the first step is analogous to that catalyzed by serine dehydratase, foods high in threonine include cottage cheese, poultry, fish, meat, lentils, Black turtle bean and Sesame seeds. Racemic threonine can be prepared from crotonic acid by using mercury acetate. Threonine biosynthesis CID205 CID6288
10.
Isoleucine
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Isoleucine encoded by the codons ATT, ATC, ATA is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, Isoleucine is synthesized from pyruvate employing leucine biosynthesis enzymes in other organisms such as bacteria. However, in cases, MSUD can lead to damage to the brain cells. As an essential nutrient, it is not synthesized in the body, hence it must be ingested, in plants and microorganisms, it is synthesized via several steps, starting from pyruvic acid and alpha-ketoglutarate. It can also be converted into Acetyl CoA and fed into the TCA cycle by condensing with oxaloacetate to form citrate, in mammals Acetyl CoA cannot be converted back to carbohydrate but can be used in the synthesis of ketone bodies or fatty acids, hence ketogenic. Biotin, sometimes referred to as Vitamin B7 or Vitamin H, is a requirement for the full catabolism of isoleucine. Without adequate biotin, the body will be unable to fully break down isoleucine and leucine molecules. Even though this acid is not produced in animals, it is stored in high quantities. Foods that have high amounts of isoleucine include eggs, soy protein, seaweed, turkey, chicken, lamb, cheese, Isoleucine can be synthesized in a multistep procedure starting from 2-bromobutane and diethylmalonate. Synthetic isoleucine was originally reported in 1905, german chemist Felix Ehrlich discovered isoleucine in hemoglobin in 1903. Center for Biological Sequence Analysis, University of Denmark http, //www. cbs. dtu. dk/courses/27619/codon. html Isoleucine and valine biosynthesis
11.
Leucine
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Leucine is an α-amino acid used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans—meaning the body cannot synthesize it and thus must obtain from the diet, leucine is a major component of the subunits in ferritin, astacin, and other buffer proteins. Leucine is used in the liver, adipose tissue, and muscle tissue, adipose and muscle tissue use leucine in the formation of sterols. Combined leucine use in these two tissues is seven times greater than in the liver, leucine is an essential amino acid in the diet of animals because they lack the complete enzyme pathway to synthesize it de novo from potential precursor compounds. Consequently, they must ingest it, usually as a component of proteins, in healthy individuals, approximately 60% of dietary L-leucine is metabolized after several hours, with roughly 5% of dietary L-leucine being converted to β-hydroxy β-methylbutyric acid. Around 40% of dietary L-leucine is converted to acetyl-CoA, which is used in the synthesis of other compounds. The vast majority of L-leucine metabolism is initially catalyzed by the amino acid aminotransferase enzyme. α-Ketoisocaproate is mostly metabolized by the mitochondrial enzyme branched-chain α-ketoacid dehydrogenase, isovaleryl-CoA is subsequently metabolized by isovaleryl-CoA dehydrogenase and converted to β-methylcrotonoyl-CoA, which is used in the synthesis of acetyl-CoA and other compounds. A relatively small amount of α-KIC is metabolized in the liver by the cytosolic enzyme 4-hydroxyphenylpyruvate dioxygenase, in healthy individuals, this minor pathway – which involves the conversion of L-leucine to α-KIC and then HMB – is the predominant route of HMB synthesis. HMB could be produced via certain metabolites that are generated along this pathway, the metabolism of HMB is initially catalyzed by an uncharacterized enzyme which converts it to HMB-CoA. HMB-CoA is metabolized by either enoyl-CoA hydratase or another uncharacterized enzyme, MC-CoA is then converted by the enzyme methylcrotonyl-CoA carboxylase to methylglutaconyl-CoA, which is subsequently converted to HMG-CoA by methylglutaconyl-CoA hydratase. HMG-CoA is then cleaved into to acetyl-CoA and acetoacetate by HMG-CoA lyase or used in the production of cholesterol via the mevalonate pathway and it is a dietary amino acid with the capacity to directly stimulate muscle protein synthesis. As a dietary supplement, leucine has been found to slow the degradation of tissue by increasing the synthesis of muscle proteins in aged rats. However, results of studies are conflicted. Long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men, more studies are needed, preferably ones based on an objective, random sample of society. Until then, dietary supplemental leucine cannot be associated as the reason for muscular growth or optimal maintenance for the entire population. Leucine potently activates the mammalian target of rapamycin kinase that regulates cell growth, infusion of leucine into the rat brain has been shown to decrease food intake and body weight via activation of the mTOR pathway
12.
Lysine
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Lysine, encoded by the codons AAA and AAG, is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, lysine is a base, as are arginine and histidine. The ε-amino group often participates in hydrogen bonding and as a base in catalysis. The ε-amino group is attached to the carbon from the α-carbon. O-Glycosylation of hydroxylysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell, deficiencies may cause blindness, as well as many other problems due to its ubiquitous presence in proteins. As an essential amino acid, lysine is not synthesized in animals, in plants and most bacteria, it is synthesized from aspartic acid, L-aspartate is first converted to L-aspartyl-4-phosphate by aspartokinase. ATP is needed as a source for this step. β-Aspartate semialdehyde dehydrogenase converts this into β-aspartyl-4-semialdehyde, energy from NADPH is used in this conversion. 4-hydroxy-tetrahydrodipicolinate synthase adds a pyruvate group to the β-aspartyl-4-semialdehyde, and a molecule is removed. This causes cyclization and gives rise to -4-hydroxy-2,3,4 and this product is reduced to 2,3,4, 5-tetrahydrodipicolinate by 4-hydroxy-tetrahydrodipicolinate reductase. This reaction consumes an NADPH molecule and releases a water molecule. Tetrahydrodipicolinate N-acetyltransferase opens this ring and gives rise to N-succinyl-L-2-amino-6-oxoheptanedionate, two water molecules and one acyl-CoA enzyme are used in this reaction. This reaction is catalyzed by the enzyme succinyl diaminopimelate aminotransferase, a glutamic acid molecule is used in this reaction and an oxoacid is produced as a byproduct. N-succinyl-LL-2, 6-diaminoheptanedionate is converted into LL-2, 6-diaminoheptanedionate by succinyl diaminopimelate desuccinylase, a water molecule is consumed in this reaction and a succinate is produced a byproduct. LL-2, 6-diaminoheptanedionate is converted by diaminopimelate epimerase into meso-2, 6-diamino-heptanedionate, finally, meso-2, 6-diamino-heptanedionate is converted into L-lysine by diaminopimelate decarboxylase. It is worth noting, however, that in fungi, euglenoids, lysine is metabolised in mammals to give acetyl-CoA, via an initial transamination with α-ketoglutarate. The bacterial degradation of lysine yields cadaverine by decarboxylation, allysine is a derivative of lysine, used in the production of elastin and collagen
13.
Methionine
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Methionine is an essential amino acid in humans. Overconsumption of methionine, as is typical in the standard American diet, Methionine was first isolated in 1921 by John Howard Mueller. Methionine is an acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. Methionine is coded for by the initiation codon, meaning it indicates the start of the region and is the first amino acid produced in a nascent polypeptide during mRNA translation. Together with cysteine, methionine is one of two sulfur-containing proteinogenic amino acids, excluding the few exceptions where methionine may act as a redox sensor, methionine residues do not have a catalytic role. This is in contrast to cysteine residues, where the group has a catalytic role in many proteins. This situation is not unique and may have occurred with ornithine and arginine, Methionine is one of only two amino acids encoded by a single codon in the standard genetic code. In reflection to the origin of its codon, the other AUN codons encode isoleucine. In the mitochondrial genome of several organisms, including metazoa and yeast, in the standard genetic code AUA codes for isoleucine and the respective tRNA uses the unusual base lysidine or agmatine to discriminate against AUG. The methionine codon AUG is also the most common start codon, a Start codon is message for a ribosome that signals the initiation of protein translation from mRNA when the AUG codon is in a Kozak consensus sequence. In bacteria, the derivative N-formylmethionine is used as the amino acid. The methionine-derivative S-adenosyl methionine is a cofactor that serves mainly as a methyl donor, SAM is composed of an adenosyl molecule attached to the sulfur of methionine, therefore making it a sulfonium cation. The sulfur acts as soft Lewis acid allows the S-methyl group to be transferred to an oxygen, nitrogen or aromatic system, some enzymes use SAM to initiate a radical reaction, these are called radical SAM enzymes. As a result of the transfer of the group, S-adenosyl-homocysteine is obtained. As an essential amino acid, methionine is not synthesized de novo in humans and other animals, in plants and microorganisms, methionine biosynthesis belongs to the aspartate family, along with threonine and lysine. The main backbone is derived from acid, while the sulfur may come from cysteine. First, aspartic acid is converted via β-aspartyl-semialdehyde into homoserine by two steps of the terminal carboxyl group
14.
Cystine
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Cystine is the oxidized dimer form of the amino acid cysteine and has the formula 2. It is a solid that is slightly soluble in water. It serves two functions, a site of redox reactions and a mechanical linkage that allows proteins to retain their 3-dimensional structure. It is common in many such as eggs, meat, dairy products. It was not recognized as being derived of proteins until it was isolated from the horn of a cow in 1899, human hair and skin contain approximately 10–14% cystine by mass. It was discovered in 1810 by William Hyde Wollaston and it is formed from the oxidation of two cysteine molecules, via the formation of a disulfide bond. In cell biology, cystine can only exist in non-reductive organelles, meaning that in reductive conditions cysteine is favorably found. The disulfide link is readily reduced to give the corresponding thiol cysteine, disulfide bonds cleave more rapidly at higher temperatures. The presence of cystine in urine is often indicative of amino acid reabsorption defects, cystinuria has been reported to occur in dogs. In humans the excretion of high levels of cystine crystals can be indicative of cystinosis, cystine serves as a substrate for the cystine-glutamate antiporter. This transport system, which is specific for cystine and glutamate. In this system, the form of cystine is transported in exchange for glutamate. Cystine is quickly reduced to cysteine, cysteine prodrugs, e. g. acetylcysteine, induce release of glutamate into the extracellular space. Cysteine supplements are marketed as anti-aging products with claims of improved skin elasticity. Cysteine is more easily absorbed by the body than cystine, so most supplements contain cysteine rather than cystine, n-acetyl-cysteine is better absorbed than other cysteine or cystine supplements. Lanthionine, similar with mono-sulfide link Protein tertiary structure Sullivan reaction
15.
Phenylalanine
–
Phenylalanine is an α-amino acid with the formula C 9H 11NO2. It can be viewed as a benzyl group substituted for the group of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert, the L-isomer is used to biochemically form proteins, coded for by DNA. The codons for L-phenylalanine are UUU and UUC, Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine, and epinephrine, and the skin pigment melanin. Phenylalanine is found naturally in the breast milk of mammals and it is used in the manufacture of food and drink products and sold as a nutritional supplement for its reputed analgesic and antidepressant effects. It is a precursor to the neuromodulator phenethylamine, a commonly used dietary supplement. The first description of phenylalanine was made in 1879, when Schulze and Barbieri identified a compound with the formula, C9H11NO2. In 1882, Erlenmeyer and Lipp first synthesized phenylalanine from phenylacetaldehyde, hydrogen cyanide, the genetic codon for phenylalanine was first discovered by J. Heinrich Matthaei and Marshall W. Nirenberg in 1961. This discovery helped to establish the nature of the relationship that links information stored in genomic nucleic acid with protein expression in the living cell. As an essential amino acid, phenylalanine is not synthesized de novo in humans and other animals, good sources of phenylalanine are eggs, chicken, liver, beef, milk, and soybeans. L-Phenylalanine is biologically converted into L-tyrosine, another one of the DNA-encoded amino acids, L-tyrosine in turn is converted into L-DOPA, which is further converted into dopamine, norepinephrine, and epinephrine. The latter three are known as the catecholamines, Phenylalanine uses the same active transport channel as tryptophan to cross the blood–brain barrier. The corresponding enzymes in for those compounds are the amino acid hydroxylase family. Phenylalanine is the compound used in the synthesis of flavonoids. Lignan is derived from phenylalanine and from tyrosine, Phenylalanine is converted to cinnamic acid by the enzyme phenylalanine ammonia-lyase. The genetic disorder phenylketonuria is the inability to metabolize phenylalanine because of a lack of the enzyme phenylalanine hydroxylase, individuals with this disorder are known as phenylketonurics and must regulate their intake of phenylalanine. A variant form of phenylketonuria called hyperphenylalaninemia is caused by the inability to synthesize a cofactor called tetrahydrobiopterin, pregnant women with hyperphenylalaninemia may show similar symptoms of the disorder but these indicators will usually disappear at the end of gestation. Pregnant women with PKU must control their blood phenylalanine levels even if the fetus is heterozygus for the defective gene because the fetus could be affected due to hepatic immaturity
16.
Tyrosine
–
Tyrosine or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is an amino acid with a polar side group. Its codons are UAC and UAU, the word tyrosine is from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a group or side chain. Aside from being an amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes and it functions as a receiver of phosphate groups that are transferred by way of protein kinases. Phosphorylation of the group changes the activity of the target protein. A tyrosine residue plays a important role in photosynthesis. In chloroplasts, it acts as a donor in the reduction of oxidized chlorophyll. In this process, it loses the hydrogen atom of its phenolic OH-group and this radical is subsequently reduced in the photosystem II by the four core manganese clusters. The Recommended Dietary Allowance for phenylalanine and tyrosine is 33 mg per kilogram of body weight, for a 70 kg person this is 2310 mg. For example, the white of an egg has about 250 mg per egg, in plants and most microorganisms, tyr is produced via prephenate, an intermediate on the shikimate pathway. Mammals synthesize tyrosine from the amino acid phenylalanine, which is derived from food. The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase and this enzyme catalyzes the reaction causing the addition of a hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine, such that it becomes tyrosine. Some of the residues can be tagged with a phosphate group by protein kinases. In its phosphorylated form, tyrosine is called phosphotyrosine, tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies, tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation. Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase, like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine
17.
Valine
–
Valine encoded by the codons GUU, GUC, GUA, and GUG is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is essential in humans, meaning the body cannot synthesize it, human dietary sources are any proteinaceous foods such as meats, dairy products, soy products, beans and legumes. Along with leucine and isoleucine, valine is an amino acid. In sickle-cell disease, valine substitutes for the amino acid glutamic acid in β-globin. Because valine is hydrophobic, the hemoglobin is prone to abnormal aggregation, Valine was first isolated from casein in 1901 by Hermann Emil Fischer. The name valine comes from valeric acid, which in turn is named after the plant valerian due to the presence of the acid in the roots of the plant. According to IUPAC, carbon atoms forming valine are numbered starting from 1 denoting the carboxyl carbon. Valine is an amino acid, hence it must be ingested. It is synthesized in plants via several steps starting from pyruvic acid, the initial part of the pathway also leads to leucine. The intermediate α-ketoisovalerate undergoes reductive amination with glutamate, orten and Otto W. Neuhaus, pages 367-368. Mice fed a valine free diet for one day have improved insulin sensitivity, the valine catabolite 3-hydroxyisobutyrate promotes skeletal muscle insulin resistance in mice by stimulating fatty acid uptake into muscle and lipid accumulation. In humans, a restricted diet lowers blood levels of valine. Experiments in mice have shown that dietary valine is essential for hematopoetic stem cell self-renewal, dietary valine restriction selectively depletes long-term repopulating Hematopoetic Stem Cells in mouse Bone Marrow. Successful stem cell transplantation was achieved in mice without irradiation after 3 weeks on a -Val diet, long term survival of the transplanted mice was achieved when valine was returned to the diet gradually over a 2 week period to avoid refeeding syndrome. Valinol Valine MS Spectrum Isoleucine and valine biosynthesis Valines relationship to prions
18.
Histidine
–
Histidine is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, a carboxylic acid group. Initially thought essential only for infants, longer-term studies have shown it is essential for adults also, Histidine was first isolated by German physician Albrecht Kossel and Sven Hedin in 1896. It is also a precursor to histamine, an inflammatory agent in immune responses. The conjugate acid of the side chain in histidine has a pKa of approximately 6.0. This means that, at physiologically relevant pH values, relatively small shifts in pH will change its average charge, below a pH of 6, the imidazole ring is mostly protonated as described by the Henderson–Hasselbalch equation. When protonated, the ring bears two NH bonds and has a positive charge. The positive charge is distributed between both nitrogens and can be represented with two equally important resonance structures. As the pH increases past approximately 6, one of the protons is lost, the remaining proton of the now-neutral imidazole ring can reside on either nitrogen, giving rise to what are known as the N1-H or N3-H tautomers. When both imidazole ring nitrogens are protonated, their 15N chemical shifts are similar, NMR shows that the chemical shift of N1-H drops slightly, whereas the chemical shift of N3-H drops considerably. This indicates that the N1-H tautomer is preferred, it is presumed due to hydrogen bonding to the neighboring ammonium, as the pH rises above 9, the chemical shifts of N1 and N3 become approximately 185 and 170 ppm. An entirely deprotonated form of the ring, the imidazolate ion, would be formed only above a pH of 14. This change in chemical shifts can be explained by the presumably decreased hydrogen bonding of an amine over an ammonium ion, and this should act to decrease the N1-H tautomer preference. The imidazole ring of histidine is aromatic at all pH values and it contains six pi electrons, four from two double bonds and two from a nitrogen lone pair. It can form pi stacking interactions, but is complicated by the positive charge and it does not absorb at 280 nm in either state, but does in the lower UV range more than some amino acids. The imidazole sidechain of histidine is a coordinating ligand in metalloproteins and is a part of catalytic sites in certain enzymes. It has the ability to switch between protonated and unprotonated states, which allows histidine to participate in acid-base catalysis, in catalytic triads, the basic nitrogen of histidine is used to abstract a proton from serine, threonine, or cysteine to activate it as a nucleophile. In a histidine proton shuttle, histidine is used to quickly shuttle protons and it can do this by abstracting a proton with its basic nitrogen to make a positively charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen
19.
Alanine
–
Alanine is an α-amino acid that is used in the biosynthesis of proteins. It contains a group, an α-carboxylic acid group. It is non-essential in humans, meaning the body can synthesize it, the L-isomer of alanine is one of the 20 amino acids encoded by the human genetic code. L-Alanine is second only to leucine in rate of occurrence, accounting for 7. 8% of the structure in a sample of 1,150 proteins. The right-handed form, D-Alanine occurs in bacterial cell walls and in some peptide antibiotics, Alanine was first isolated in 1879 by Adolph Strecker. The amino acid was named Alanin in German, in reference to aldehyde, with the infix -an- for ease of pronunciation, the German ending -in used in chemical compounds being analogous to English -ine. The α-carbon atom of alanine is bound to a group, making it one of the simplest α-amino acids. The methyl group of alanine is non-reactive and is thus almost never directly involved in protein function, Alanine is an amino acid that cannot be phosphorylated, making it quite useful in a loss of function experiment with respect to phosphorylation. Alanine is an amino acid, meaning it can be manufactured by the human body. Alanine is found in a variety of foods, but is particularly concentrated in meats. Alanine can be manufactured in the body from pyruvate and branched chain amino acids such as valine, leucine, Alanine is most commonly produced by reductive amination of pyruvate. It also arises together with lactate and generates glucose from protein via the alanine cycle, in muscle and other tissues that degrade amino acids for fuel, amino groups are collected in the form of glutamate by transamination. Glutamate can then transfer its amino group through the action of alanine aminotransferase to pyruvate, the alanine formed is passed into the blood and transported to the liver. A reverse of the alanine aminotransferase reaction takes place in liver, pyruvate regenerated forms glucose through gluconeogenesis, which returns to muscle through the circulation system. Glutamate in the liver enters mitochondria and degrades into ammonium ion through the action of glutamate dehydrogenase, the glucose–alanine cycle enables pyruvate and glutamate to be removed from the muscle and find their way to the liver. Glucose is regenerated from pyruvate and then returned to muscle, the burden of gluconeogenesis is thus imposed on the liver instead of the muscle. All available ATP in muscle is devoted to muscle contraction, an international study led by Imperial College London found a correlation between high levels of alanine and higher blood pressure, energy intake, cholesterol levels, and body mass index. Alterations in the cycle that increase the levels of serum alanine aminotransferase is linked to the development of type II diabetes
20.
Aspartic acid
–
Aspartic acid, also known as aspartate, is an α-amino acid that is used in the biosynthesis of proteins. Similar to all other amino acids it contains an amino group and its α-amino group is in the protonated –NH+3 form under physiological conditions, while its α-carboxylic acid group is deprotonated −COO− under physiological conditions. Aspartic acid has a side chain which reacts with other amino acids, enzymes. Under physiological conditions in proteins the side chain usually occurs as the negatively charged aspartate form and it is a non-essential amino acid in humans, meaning the body can synthesize it as needed. D-Aspartate is one of two D-amino acids commonly found in mammals, in proteins aspartate sidechains are often hydrogen bonded, often as asx turns or asx motifs, which often occur at the N-termini of alpha helices. Asps L-isomer is one of the 22 proteinogenic amino acids, i. e. the building blocks of proteins. Asp is classified as acidic, with a pKa of 3.9, however in a peptide this is dependent on the local environment. Aspartic acid was first discovered in 1827 by Auguste-Arthur Plisson and Étienne Ossian Henry by hydrolysis of asparagine and their original method used lead hydroxide, but various other acids or bases are more commonly used instead. There are two forms or enantiomers of aspartic acid, the name aspartic acid can refer to either enantiomer or a mixture of two. Of these two forms, only one, L-aspartic acid, is incorporated into proteins. The biological roles of its counterpart, D-aspartic acid are more limited, where enzymatic synthesis will produce one or the other, most chemical syntheses will produce both forms, DL-aspartic acid, known as a racemic mixture. Because Aspartate can be synthesized by the body it is classified as an amino acid. In the human body, aspartate is most frequently synthesized through the transamination of oxaloacetate, the biosynthesis of aspartate is facilitated by an aminotransferase enzyme, the transfer of an amine group from another molecule such as alanine or glutamine yields aspartate and an alpha-keto acid. Aspartate is also a byproduct of the urea cycle, racemic aspartic acid can be synthesized from diethyl sodium phthalimidomalonate. The major disadvantage of the technique is that equimolar amounts of each enantiomer are made. Using biotechnology it is now possible to use immobilised enzymes to create just one type of enantiomer owing to their stereospecificity. In plants and microorganisms, aspartate is the precursor to several amino acids, including four that are essential for humans, methionine, threonine, isoleucine, the conversion of aspartate to these other amino acids begins with reduction of aspartate to its semialdehyde, O2CCHCH2CHO. Asparagine is derived from aspartate via transamidation, -O2CCHCH2CO2- + GCNH3+ O2CCHCH2CONH3+ + GCO In the urea cycle, aspartate, Aspartate has many other biochemical roles
21.
Glutamic acid
–
Glutamic acid is an α-amino acid with formula C 5H 9O 4N. It is usually abbreviated as Glu or E in biochemistry and its molecular structure could be idealized as HOOC-CH-2-COOH, with two carboxyl groups -COOH and one amino group -NH2. However, in the state and mildly acid water solutions. Glutamic acid is used by almost all living beings in the biosynthesis of proteins and it is non-essential in humans, meaning the body can synthesize it. The acid can lose one proton from second carboxyl group to form the conjugate base and this form of the compound is prevalent in neutral solutions. The glutamate neurotransmitter plays the role in neural activation. This anion is also responsible for the flavor of certain foods. In highly alkaline solutions the doubly negative anion −OOC-CH-2-COO− prevails, the radical corresponding to glutamate is called glutamyl. When glutamic acid is dissolved in water, the group may gain a proton, and/or the carboxyl groups may lose protons. In sufficiently acid environments, the group gains a proton. At pH values between about 2.5 and 4.1, the carboxylic acid closer to the amine generally loses a proton, and the acid becomes the neutral zwitterion −OOC-CH-2-COOH. This is also the form of the compound in the solid state. The switchover is gradual, the two forms are in equal concentrations at pH2.10, at even higher pH, the other carboxyl loses its proton and the acid exists almost entirely as the glutamate anion −OOC-CH-2-COO−, with a single negative charge. The switchover occurs at pH4.07, the latter is the case, in particular, in the physiological pH range. At even higher pH, the group loses the extra proton. The switchover occurs at pH9.47, the carbon atom adjacent to the amino group is chiral, so glutamic acid can exist in two optical isomers, D and L. The L form is the one most widely occurring in nature, but the D form occurs in special contexts, such as the cell walls of the bacterium Escherichia coli. Although they occur naturally in foods, the flavor contributions made by glutamic acid
22.
Glycine
–
Glycine is the amino acid that has a single hydrogen atom as its side chain. It is the simplest possible amino acid, the chemical formula of glycine is NH2‐CH2‐COOH. Glycine is one of the amino acids. Its codons are GGU, GGC, GGA, GGG of the genetic code, Glycine is a colorless, sweet-tasting crystalline solid. It is unique among the amino acids in that it is achiral. It can fit into hydrophilic or hydrophobic environments since it exists as zwitterion at natural pH, Glycine was first isolated from gelatin in 1820. The name comes from the ancient Greek word γλυκύς sweet tasting, Glycine was discovered in 1820, by Henri Braconnot who boiled a gelatinous object with sulfuric acid. Glycine is manufactured industrially by treating chloroacetic acid with ammonia, ClCH2COOH +2 NH3 → H2NCH2COOH + NH4Cl About 15 million kg are produced annually in this way, in the USA and in Japan, glycine is produced via the Strecker amino acid synthesis. Glycine is also cogenerated as an impurity in the synthesis of EDTA, arising from reactions of the ammonia coproduct. In aqueous solution, glycine itself is amphoteric, at low pH the molecule can be protonated with a pKa of about 2.4, the nature of glycine in aqueous solution has been investigated by theoretical methods. In solution the ratio of concentrations of the two isomers is independent of both the concentration and of pH. This ratio is simply the equilibrium constant for isomerization, K = / Both isomers of glycine have been observed by microwave spectroscopy in the gas phase. The solid-state structure has been analyzed in detail and this conversion is readily reversible, CO2 + NH+4 + N5, N10-Methylene tetrahydrofolate + NADH + H+ → Glycine + tetrahydrofolate + NAD+ Glycine is coded by codons GGU, GGC, GGA and GGG. Most proteins incorporate only small quantities of glycine, a notable exception is collagen, which contains about 35% glycine. Glycine is degraded via three pathways, the first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase, in the third pathway of glycine degradation, glycine is converted to glyoxylate by D-amino acid oxidase. Glyoxylate is then oxidized by lactate dehydrogenase to oxalate in an NAD+-dependent reaction. The half-life of glycine and its elimination from the body varies significantly based on dose, in one study, the half-life was between 0.5 and 4.0 hours
23.
Serine
–
Serine encoded by the codons UCU, UCC, UCA, UCG, AGU and AGC is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains a group, a carboxyl group, and a side chain consisting of a hydroxymethyl group. It can be synthesized in the body under normal physiological circumstances. This compound is one of the naturally occurring amino acids. Only the L-stereoisomer appears naturally in proteins and it is not essential to the human diet, since it is synthesized in the body from other metabolites, including glycine. Serine was first obtained from silk protein, a rich source. Its name is derived from the Latin for silk, sericum, serines structure was established in 1902. The biosynthesis of serine starts with the oxidation of 3-phosphoglycerate to 3-phosphohydroxypyruvate, reductive amination of this ketone by phosphoserine transaminase yields 3-phosphoserine which is hydrolyzed to serine by phosphoserine phosphatase. In bacteria such as E. coli these enzymes are encoded by the genes serA, serC, glycine biosynthesis, Serine hydroxymethyltransferase also catalyzes the reversible conversions of L-serine to glycine and 5,6,7, 8-tetrahydrofolate to 5, 10-methylenetetrahydrofolate. SHMT is a pyridoxal phosphate dependent enzyme, glycine can also be formed from CO2, NH4+, and mTHF in a reaction catalyzed by glycine synthase. Industrially, L-serine is produced by fermentation, with an estimated 100-1000 tonnes per year produced, in the laboratory, racemic serine can be prepared from methyl acrylate via several steps, Serine is important in metabolism in that it participates in the biosynthesis of purines and pyrimidines. It is the precursor to several amino acids including glycine and cysteine and it is also the precursor to numerous other metabolites, including sphingolipids and folate, which is the principal donor of one-carbon fragments in biosynthesis. Serine plays an important role in the function of many enzymes. It has been shown to occur in the sites of chymotrypsin, trypsin. Serine sidechains are often bonded, the commonest small motifs formed are ST turns, ST motifs. As a constituent of proteins, its side chain can undergo O-linked glycosylation and it is one of three amino acid residues that are commonly phosphorylated by kinases during cell signaling in eukaryotes. Phosphorylated serine residues are often referred to as phosphoserine, Serine proteases are a common type of protease. D-Serine, synthesized in the brain by serine racemase from L-serine, serves as a neuromodulator by coactivating NMDA receptors, D-serine is a potent agonist at the glycine site of the NMDA-type glutamate receptor
24.
Vitamin
–
A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. For example, ascorbic acid is a vitamin for humans, supplementation is important for the treatment of certain health problems, but there is little evidence of nutritional benefit when used by otherwise healthy people. Thirteen vitamins are universally recognized at present, Vitamins are classified by their biological and chemical activity, not their structure. Thus, each vitamin refers to a number of compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals is grouped under an alphabetized vitamin generic descriptor title, such as vitamin A, which includes the compounds retinal, retinol, and four known carotenoids. Vitamers by definition are convertible to the form of the vitamin in the body. Some, such as vitamin D, have hormone-like functions as regulators of mineral metabolism, or regulators of cell and tissue growth and differentiation. The largest number of vitamins, the B complex vitamins, function as cofactors or the precursors for them. In this role, vitamins may be bound to enzymes as part of prosthetic groups, For example. They may also be less tightly bound to enzyme catalysts as coenzymes, for example, folic acid may carry methyl, formyl, and methylene groups in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins best-known function, study of structural activity, function and their role in maintaining health is called vitaminology. Each vitamin is typically used in reactions, and therefore most have multiple functions. Vitamins are essential for the growth and development of a multicellular organism. Using the genetic blueprint inherited from its parents, a fetus begins to develop from the nutrients it absorbs and it requires certain vitamins and minerals to be present at certain times. These nutrients facilitate the chemical reactions that produce among other things, skin, bone, if there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage, for the most part, vitamins are obtained with food, but a few are obtained by other means. Humans can produce some vitamins from precursors they consume, examples include vitamin A, produced from beta carotene, and niacin, from the amino acid tryptophan. In those who are healthy, there is little evidence that supplements have any benefits with respect to cancer or heart disease
25.
Vitamin A
–
Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids. Vitamin A has multiple functions, it is important for growth and development, for the maintenance of the immune system and good vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, Vitamin A also functions in a very different role as retinoic acid, which is an important hormone-like growth factor for epithelial and other cells. In foods of animal origin, the form of vitamin A is an ester, primarily retinyl palmitate. The retinol form functions as a form of the vitamin. All forms of vitamin A have a ring to which an isoprenoid chain is attached, called a retinyl group. Both structural features are essential for vitamin activity, the orange pigment of carrots can be represented as two connected retinyl groups, which are used in the body to contribute to vitamin A levels. Alpha-carotene and gamma-carotene also have a single group, which give them some vitamin activity. None of the other carotenes have vitamin activity, the carotenoid beta-cryptoxanthin possesses an ionone group and has vitamin activity in humans. Vitamin A can be found in two forms in foods, Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow. Since the pure form is unstable, the vitamin is found in tissues in a form of retinyl ester. It is also produced and administered as esters such as retinyl acetate or palmitate. Vitamin A deficiency is estimated to approximately one third of children under the age of five around the world. It is estimated to claim the lives of 670,000 children under five annually, approximately 250, 000–500,000 children in developing countries become blind each year owing to vitamin A deficiency, with the highest prevalence in Southeast Asia and Africa. Vitamin A deficiency is the cause of preventable childhood blindness. It also increases the risk of death from common childhood conditions such as diarrhea, UNICEF regards addressing vitamin A deficiency as critical to reducing child mortality, the fourth of the United Nations Millennium Development Goals. Vitamin A deficiency can occur as either a primary or a secondary deficiency, early weaning from breastmilk can also increase the risk of vitamin A deficiency. Vitamin A is a vitamin and depends on micellar solubilization for dispersion into the small intestine
26.
Human iron metabolism
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Human iron metabolism is the set of chemical reactions maintaining human homeostasis of iron at both the systemic and cellular level. The control of this necessary but potentially toxic metal is an important part of many aspects of human health, hematologists have been especially interested in systemic iron metabolism because iron is essential for red blood cells, where most of the human bodys iron is contained. Understanding iron metabolism is also important for understanding diseases of iron overload, such as hereditary hemochromatosis, iron is an essential bioelement for most forms of life, from bacteria to mammals. Its importance lies in its ability to mediate electron transfer, in the ferrous state, iron acts as an electron donor, while in the ferric state it acts as an acceptor. Thus, iron plays a role in the catalysis of enzymatic reactions that involve electron transfer. Proteins can contain iron as part of different cofactors, such as clusters and heme groups. Human cells require iron in order to obtain energy as ATP from a process known as cellular respiration. Iron is present in the clusters and heme groups of the electron transport chain proteins that generate a proton gradient that allows ATP synthase to synthesize ATP. Heme groups are part of hemoglobin, a found in red blood cells that serves to transport oxygen from the lungs to the tissues. Heme groups are present in myoglobin to store and diffuse oxygen in muscle cells. The human body needs iron for oxygen transport, oxygen is required for the functioning and survival of nearly all cell types. Oxygen is transported from the lungs to the rest of the bound to the heme group of hemoglobin in erythrocytes. In muscles cells, iron binds myoglobin, which regulates its release and its ability to donate and accept electrons means that it can catalyze the conversion of hydrogen peroxide into free radicals. Free radicals can cause damage to a variety of cellular structures. Iron bound to proteins or cofactors such as heme is safe, also, there are virtually no truly free iron ions in the cell, since they readily form complexes with organic molecules. However, some of the iron is bound to low-affinity complexes. Iron in such complexes can cause damage as described above, to prevent that kind of damage, all life forms that use iron bind the iron atoms to proteins. This binding allows cells to benefit from iron while also limiting its ability to do harm, in mammalian cells, intracellular labile iron concentrations are typically smaller than 1 micromolar, less than 5 percent of total cellular iron
27.
Kilogram
–
The kilogram or kilogramme is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype of the Kilogram. The avoirdupois pound, used in both the imperial and US customary systems, is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds. Other traditional units of weight and mass around the world are also defined in terms of the kilogram, the gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimeter of water at the melting point of ice. The final kilogram, manufactured as a prototype in 1799 and from which the IPK was derived in 1875, had an equal to the mass of 1 dm3 of water at its maximum density. The kilogram is the only SI base unit with an SI prefix as part of its name and it is also the only SI unit that is still directly defined by an artifact rather than a fundamental physical property that can be reproduced in different laboratories. Three other base units and 17 derived units in the SI system are defined relative to the kilogram, only 8 other units do not require the kilogram in their definition, temperature, time and frequency, length, and angle. At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, the decision was originally deferred until 2014, in 2014 it was deferred again until the next meeting. There are currently several different proposals for the redefinition, these are described in the Proposed Future Definitions section below, the International Prototype Kilogram is rarely used or handled. In the decree of 1795, the term gramme thus replaced gravet, the French spelling was adopted in the United Kingdom when the word was used for the first time in English in 1797, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with kilogram having become by far the more common, UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has used to mean both kilogram and kilometer. In 1935 this was adopted by the IEC as the Giorgi system, now known as MKS system. In 1948 the CGPM commissioned the CIPM to make recommendations for a practical system of units of measurement. This led to the launch of SI in 1960 and the subsequent publication of the SI Brochure, the kilogram is a unit of mass, a property which corresponds to the common perception of how heavy an object is. Mass is a property, that is, it is related to the tendency of an object at rest to remain at rest, or if in motion to remain in motion at a constant velocity. Accordingly, for astronauts in microgravity, no effort is required to hold objects off the cabin floor, they are weightless. However, since objects in microgravity still retain their mass and inertia, the ratio of the force of gravity on the two objects, measured by the scale, is equal to the ratio of their masses. On April 7,1795, the gram was decreed in France to be the weight of a volume of pure water equal to the cube of the hundredth part of the metre
28.
Chicken
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The chicken is a type of domesticated fowl, a subspecies of the red junglefowl. It is one of the most common and widespread domestic animals, humans keep chickens primarily as a source of food, consuming both their meat and their eggs. From India, the chicken was imported to Lydia in western Asia Minor. In the UK and Ireland adult male chickens over the age of one year are known as cocks, whereas in America, Australia. Males less than a year old are cockerels, females over a year old are known as hens and younger females as pullets although in the egg-laying industry, a pullet becomes a hen when she begins to lay eggs at 16 to 20 weeks of age. In Australia and New Zealand, there is a generic term chook /ˈtʃʊk/ to describe all ages, the young are called chicks and the meat is called chicken. Chicken originally referred to domestic fowl. The species as a whole was then called domestic fowl, or just fowl. This use of chicken survives in the phrase Hen and Chickens, sometimes used as a British public house or theatre name, the word chicken is sometimes erroneously construed to mean females exclusively, despite the term hen for females being in wide circulation. In the Deep South of the United States chickens are also referred to by the slang term yardbird, in the wild, they often scratch at the soil to search for seeds, insects and even animals as large as lizards, small snakes or young mice. Chickens may live for five to ten years, depending on the breed, the worlds oldest chicken was a hen which died of heart failure at the age of 16 according to Guinness World Records. However, in some breeds, such as the Sebright chicken, the rooster has only slightly pointed neck feathers, the identification can be made by looking at the comb, or eventually from the development of spurs on the males legs. Adult chickens have a fleshy crest on their heads called a comb, or cockscomb, collectively, these and other fleshy protuberances on the head and throat are called caruncles. Both the adult male and female have wattles and combs, a muff or beard is a mutation found in several chicken breeds which causes extra feathering under the chickens face, giving the appearance of a beard. Domestic chickens are not capable of long distance flight, although birds are generally capable of flying for short distances. Chickens may occasionally fly briefly to explore their surroundings, but generally do so only to flee perceived danger, Chickens are gregarious birds and live together in flocks. They have an approach to the incubation of eggs and raising of young. Individual chickens in a flock will dominate others, establishing an order, with dominant individuals having priority for food access
29.
Poultry
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Poultry are domesticated birds kept by humans for the eggs they produce, their meat, or their feathers. These birds are most typically members of the superorder Galloanserae, especially the order Galliformes, if there are ducks and or geese that are kept as pets they shall not be considered poultry unlike domesticated chickens. Poultry also includes other birds that are killed for their meat, such as the young of pigeons but does not include wild birds hunted for sport or food. The word poultry comes from the French/Norman word poule, itself derived from the Latin word pullus, the domestication of poultry took place several thousand years ago. This may have originally been as a result of people hatching and rearing young birds from eggs collected from the wild, but later involved keeping the birds permanently in captivity. Domesticated chickens may have used for cockfighting at first and quail kept for their songs. Selective breeding for fast growth, egg-laying ability, conformation, plumage and docility took place over the centuries, although some birds are still kept in small flocks in extensive systems, most birds available in the market today are reared in intensive commercial enterprises. Poultry is the second most widely eaten type of meat globally and, along with eggs, all poultry meat should be properly handled and sufficiently cooked in order to reduce the risk of food poisoning. The word poultry comes from the Middle English pultrie, from Old French pouletrie, from pouletier, poultry dealer, the word pullet itself comes from Middle English pulet, from Old French polet, both from Latin pullus, a young fowl, young animal or chicken. The word fowl is of Germanic origin, poultry can be defined as domestic fowls, including chickens, turkeys, geese and ducks, raised for the production of meat or eggs and the word is also used for the flesh of these birds used as food. The Encyclopædia Britannica lists the bird groups but also includes guinea fowl. In colloquial speech, the term fowl is often used near-synonymously with domesticated chicken, or with poultry or even just bird, both words are also used for the flesh of these birds. Poultry can be distinguished from game, defined as wild birds or mammals hunted for food or sport, chickens are medium-sized, chunky birds with an upright stance and characterised by fleshy red combs and wattles on their heads. Males, known as cocks, are larger, more boldly coloured. Chickens are gregarious, omnivorous, ground-dwelling birds that in their natural surroundings search among the leaf litter for seeds, invertebrates and they seldom fly except as a result of perceived danger, preferring to run into the undergrowth if approached. Todays domestic chicken is descended from the wild red junglefowl of Asia. Domestication is believed to have taken place between 7,000 and 10,000 years ago, and what are thought to be fossilized chicken bones have been found in northeastern China dated to around 5,400 BC. Archaeologists believe domestication was originally for the purpose of cockfighting, the bird being a doughty fighter
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Cattle
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Cattle—colloquially cows—are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, cattle are raised as livestock for meat, as dairy animals for milk and other dairy products, and as draft animals. Other products include leather and dung for manure or fuel, in some regions, such as parts of India, cattle have significant religious meaning. From as few as 80 progenitors domesticated in southeast Turkey about 10,500 years ago, according to an estimate from 2011, in 2009, cattle became one of the first livestock animals to have a fully mapped genome. Some consider cattle the oldest form of wealth, and cattle raiding consequently one of the earliest forms of theft. Cattle were originally identified as three species, Bos taurus, the European or taurine cattle, Bos indicus, the zebu, and the extinct Bos primigenius. The aurochs is ancestral to both zebu and taurine cattle and these have been reclassified as one species, Bos taurus, with three subspecies, Bos taurus primigenius, Bos taurus indicus, and Bos taurus taurus. Complicating the matter is the ability of cattle to interbreed with other related species. Hybrid individuals and even breeds exist, not only between taurine cattle and zebu, but also one or both of these and some other members of the genus Bos – yaks, banteng. Hybrids such as the breed can even occur between taurine cattle and either species of bison, leading some authors to consider them part of the genus Bos. However, cattle cannot successfully be hybridized with more distantly related bovines such as water buffalo or African buffalo, the aurochs originally ranged throughout Europe, North Africa, and much of Asia. In historical times, its range became restricted to Europe, breeders have attempted to recreate cattle of similar appearance to aurochs by crossing traditional types of domesticated cattle, creating the Heck cattle breed. Cattle did not originate as the term for bovine animals and it was borrowed from Anglo-Norman catel, itself from medieval Latin capitale principal sum of money, capital, itself derived in turn from Latin caput head. Cattle originally meant movable personal property, especially livestock of any kind, the word is a variant of chattel and closely related to capital in the economic sense. The term replaced earlier Old English feoh cattle, property, which today as fee. The word cow came via Anglo-Saxon cū, from Common Indo-European gʷōus = a bovine animal, compare Persian gâv, Sanskrit go-, Welsh buwch. The plural cȳ became ki or kie in Middle English, and a plural ending was often added, giving kine, kien. This is the origin of the now archaic English plural, kine, the Scots language singular is coo or cou, and the plural is kye
31.
Domestic pig
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The domestic pig, often called swine, hog, or pig when there is no need to distinguish it from other pigs, is a large, even-toed ungulate. It is variously considered a subspecies of the boar or a distinct species. The domestic pigs head-plus-body-length ranges from 0.9 to 1.8 m, compared to other artiodactyls, its head is relatively long, pointed, and free of warts. Even-toed ungulates are generally herbivorous, but the pig is an omnivore. Domestic pigs are farmed primarily for the consumption of their meat called pork, the animals bones, hide, and bristles are also used in commercial products. Domestic pigs, especially the pig and micro pig, are sometimes kept as pets. The domestic pig typically has a head, with a long snout which is strengthened by a special prenasal bone. The snout is used to dig into the soil to find food, the dental formula of adult pigs is 3.1.4.33.1.4.3, giving a total of 44 teeth. The rear teeth are adapted for crushing, in the male the canine teeth can form tusks, which grow continuously and are sharpened by constantly being ground against each other. There are four hoofed toes on each foot, or trotter, most domestic pigs have rather a sparse hair covering on their skin, although woolly-coated breeds, such as the Mangalitsa, are raised. Pigs possess both apocrine and eccrine sweat glands, although the latter appear limited to the snout and dorsonasal areas, pigs, however, like other hairless mammals, do not use thermal sweat glands in cooling. Pigs are also less able than many other mammals to dissipate heat from wet mucous membranes in the mouth through panting and their thermoneutral zone is 16 to 22 °C. Pigs are one of four known species which possess mutations in the nicotinic acetylcholine receptor that protect against snake venom. Mongooses, honey badgers, hedgehogs, and pigs all have modifications to the receptor pocket which prevents the snake venom α-neurotoxin from binding and these represent four separate, independent mutations. However, in 1777, Johann Christian Polycarp Erxleben classified the domestic pig as a species from the wild boar. He gave it the name Sus domesticus, which is used by some taxonomists. Remains of pigs have been dated to earlier than 11,400 BC in Cyprus and those animals must have been introduced from the mainland, which suggests domestication in the adjacent mainland by then. There was also a separate domestication in China which took place about 8000 years ago, DNA evidence from sub-fossil remains of teeth and jawbones of Neolithic pigs shows that the first domestic pigs in Europe had been brought from the Near East
32.
Baking
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Baking is a method of cooking food that uses prolonged dry heat, normally in an oven, but also in hot ashes, or on hot stones. The most common baked item is bread but many types of foods are baked. Heat is gradually transferred from the surface of cakes, cookies, as heat travels through it transforms batters and doughs into baked goods with a firm dry crust and a softer centre. Baking can be combined with grilling to produce a hybrid barbecue variant by using both methods simultaneously, or one after the other, Baking is related to barbecuing because the concept of the masonry oven is similar to that of a smoke pit. Because of historical social and familial roles, baking has traditionally performed at home by women for domestic consumption and by men in bakeries. When production was industrialized, baking was automated by machines in large factories, the art of baking remains a fundamental skill and is important for nutrition, as baked goods, especially breads, are a common but important food, both from an economic and cultural point of view. A person who prepares baked goods as a profession is called a baker, all types of food can be baked, but some require special care and protection from direct heat. Various techniques have developed to provide this protection. In addition to bread, baking is used to prepare cakes, pastries, pies, tarts, quiches, cookies, scones, crackers, pretzels, and more. Larger cuts prepared without stuffing or coating are often roasted. Roasting, however, is suitable for finer cuts of meat. One of these is the known as en croûte, which protects the food from direct heat. Meat, poultry, game, fish or vegetables can be prepared by baking en croûte, the en croûte method also allows meat to be baked by burying it in the embers of a fire – a favourite method of cooking venison. In this case, the casing is made from a paste of flour. Salt can also be used to make a protective crust that is not eaten, another method of protecting food from the heat while it is baking, is to cook it en papillote. In this method, the food is covered by baking paper to protect it while it is being baked, the cooked parcel of food is sometimes served unopened, allowing diners to discover the contents for themselves which adds an element of surprise. Eggs can also be used in baking to produce savoury or sweet dishes, in combination with dairy products especially cheese, they are often prepared as a dessert. For example, although a baked custard can be made using starch, baked custards, such as crème caramel, are among the items that need protection from an ovens direct heat, and the bain-marie method serves this purpose
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Grilling
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Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above or below. Grilling usually involves a significant amount of direct, radiant heat, food to be grilled is cooked on a grill, a grill pan, or griddle. Heat transfer to the food when using a grill is primarily through thermal radiation, heat transfer when using a grill pan or griddle is by direct conduction. In the United States, when the source for grilling comes from above. In this case, the pan that holds the food is called a broiler pan, direct heat grilling can expose food to temperatures often in excess of 260 °C. Grilled meat acquires a distinctive roast aroma and flavor from a process called the Maillard reaction. The Maillard reaction only occurs when foods reach temperatures in excess of 155 °C, marination may reduce the formation of these compounds. Grilling is often presented as an alternative to cooking with oils, although the fat. In Japanese cities, yakitori carts, restaurants, or shops can be found and these contain charcoal-fired grills and marinated grilled meat on a stick. Yakiniku is a type of food where meat and/or vegetables are grilled directly over small charcoal or gas grills at high temperatures. In Malaysia, Singapore, Indonesia, and Thailand, a food item from food vendors is satay. In Germany, the most prominent outdoor form of grilling is using the gridiron over a bed of burning charcoal, care is taken that the charcoal does not produce flames. Often beer is sprinkled over the sausages or meat and used to suppress flames, the meat is usually marinated before grilling. Besides charcoal, sometimes gas and electric heat sources are used, other methods are used less frequently. In Argentina and Uruguay, both asado and steak a la parrilla are staple dishes and even hailed as national specialties, in Sweden, grilling directly over hot coals is the most prominent form of grilling. Usually the meat is Boston butt, pork chops or pork fillet and it is also common to cook meat and vegetables together on a skewer, this is called grillspett. In the United Kingdom, Commonwealth countries, and Ireland, grilling refers to cooking food directly under a source of direct. The grill is usually a part of an oven where the food is inserted just under the element
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Barbecue
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Barbecue or barbeque is both a cooking method and an apparatus. The word barbecue when used as a noun can refer to, the method itself, the meat cooked this way. The term is used as a verb, i. e. barbecuing is usually done outdoors by smoking the meat over wood or charcoal. Restaurant barbecue may be cooked in large, specially-designed brick or metal ovens, barbeque is practiced in many areas of the world and there are numerous regional variations. The English word barbecue and its cognates in other languages come from the Spanish word barbacoa, the Oxford English Dictionary traces the word to Haiti and translates it as a framework of sticks set upon posts. Gonzalo Fernández De Oviedo y Valdés, a Spanish explorer, was the first to use the word barbecoa in print in Spain in 1526 in the Diccionario de la Lengua Española of the Real Academia Española. After Columbus landed in the Americas in 1492, the Spaniards apparently found native Haitians roasting meat over a grill consisting of a wooden framework resting on sticks above a fire, the flames and smoke rose and enveloped the meat, giving it a certain flavor. The same framework was used as protection from nocturnal animal attacks. Traditional barbacoa involves digging a hole in the ground and placing some meat—usually a whole lamb—above a pot so the juices can be used to make a broth and it is then covered with maguey leaves and coal, and set alight. The cooking process takes a few hours, linguists have suggested the word barbacoa migrated from the Caribbean and into other languages and cultures, it moved from Caribbean dialects into Spanish, then Portuguese, French, and English. According to the OED, the first recorded use of the word in English was a verb in 1661, in Edmund Hickeringills Jamaica Viewed, Some are slain, And their flesh forthwith Barbacud and eat. The word barbecue was published in English in 1672 as a verb from the writings of John Lederer, the first known use of the word as a noun was in 1697 by the British buccaneer William Dampier. In his New Voyage Round the World, Dampier wrote, and lay there all night, upon our Borbecus, or frames of Sticks, raised about 3 foot from the Ground. The spelling barbeque is given in Merriam-Webster and the Oxford Dictionaries as a variant, in the southeastern United States, the word barbecue is used predominantly as a noun referring to roast pork, while in the southwestern states cuts of beef are often cooked. Because the word came from native groups, Europeans gave it savage connotations. However, according to Andrew Warnes, there is little proof that Hickeringills tale of cannibalism in the Caribbean is even remotely true. Today, those in the U. S. associate barbecue with classic Americana, in American English usage, grilling refers to a fast process over high heat while barbecuing refers to a slow process using indirect heat or hot smoke, similar to some forms of roasting. In a typical U. S. home grill, food is cooked on a grate directly over hot charcoal and its South American versions are the southern Brazilian churrasco and the Argentine asado
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Frying
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Frying is the cooking of food in oil or another fat. Chemically, oils and fats are the same, differing only in melting point, foods can be fried in a variety of fats, including lard, vegetable oil, rapeseed oil and olive oil. In commerce, many fats are called oils by custom, e. g. palm oil and coconut oil, a variety of foods may be fried, including the potato chip, bread, eggs and foods made from eggs, such as omelettes or pancakes. Frying is believed to have first appeared in the Ancient Egyptian kitchen, during the Old Kingdom, fats can reach much higher temperatures than water at normal atmospheric pressure. Through frying, one can sear or even carbonize the surface of foods while caramelizing sugars, the food is cooked much more quickly and has a characteristic crispness and texture. Depending on the food, the fat will penetrate it to varying degrees, contributing richness, lubricity, Frying techniques vary in the amount of fat required, the cooking time, the type of cooking vessel required, and the manipulation of the food. Sautéing, stir frying, pan frying, shallow frying, pan frying, sautéing and stir-frying involve cooking foods in a thin layer of fat on a hot surface, such as a frying pan, griddle, wok, or sauteuse. Stir frying involves frying quickly at high temperatures, requiring that the food be stirred continuously to prevent it from adhering to the cooking surface. Shallow frying is a type of pan frying using only enough fat to immerse approximately one-third to one-half of each piece of food, fat used in this technique is typically only used once. Deep-frying, on the hand, involves totally immersing the food in hot oil. Deep-frying is typically a more involved process, and may require specialized oils for optimal results. Deep frying is now the basis of a large and expanding worldwide industry. The end products can then be easily packaged for storage and distribution, examples are potato chips, french fries, nuts, doughnuts, instant noodles, etc. Media related to Frying at Wikimedia Commons
36.
Boiling
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Transition boiling is an intermediate, unstable form of boiling with elements of both types. The boiling point of water is 100 °C or 212 °F, boiling water is used as a method of making it potable by killing microbes that may be present. Clostridium spores can survive this treatment, but as the infection caused by this microbe is not water-borne, boiling is also used in cooking. Foods suitable for boiling vegetables, starchy foods such as rice, noodles and potatoes, eggs, meats, sauces, stocks. As a cooking method it is simple and suitable for large scale cookery, tough meats or poultry can be given a long, slow cooking and a nutritious stock is produced. Disadvantages include loss of water-soluble vitamins and minerals, commercially prepared foodstuffs are sometimes packed in polythene sachets and sold as boil-in-the-bag products. Nucleate boiling is characterized by the growth of bubbles or pops on a heated surface, in general, the number of nucleation sites are increased by an increasing surface temperature. An irregular surface of the vessel or additives to the fluid can create additional nucleation sites, while an exceptionally smooth surface, such as plastic. Under these conditions, a liquid may show boiling delay. As the boiling surface is heated above a temperature, a film of vapor forms on the surface. Since this vapor film is less capable of carrying heat away from the surface. The point at which this occurs is dependent on the characteristics of boiling fluid, transition boiling may be defined as the unstable boiling, which occurs at surface temperatures between the maximum attainable in nucleate and the minimum attainable in film boiling. If a surface heating the liquid is significantly hotter than the liquid then film boiling will occur, where a layer of vapor. This condition of a vapor film insulating the surface from the liquid characterizes film boiling, in distillation, boiling is used in separating mixtures. This is possible because the rising from a boiling fluid generally has a ratio of components different from that in the liquid. The elimination of micro-organisms by boiling follows first-order kinetics—at high temperatures it is achieved in time and at lower temperatures. Boiling does not ensure the elimination of all micro-organisms, the bacterial spores Clostridium can survive at 100 °C but are not water-borne or intestine affecting, thus for human health, complete sterilization of water is not required. Though the boiling point decreases with increasing altitude, it is not enough to affect the disinfecting process, boiling is the method of cooking food in boiling water, or other water-based liquids such as stock or milk
37.
Fast food
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Fast food is a type of mass-produced food that is prepared and served very quickly. The food is typically less nutritionally valuable compared to other foods, Fast food restaurants are traditionally distinguished by their ability to serve food via a drive-through. Outlets may be stands or kiosks, which may provide no shelter or seating, franchise operations that are part of restaurant chains have standardized foodstuffs shipped to each restaurant from central locations. Fast food began with the first fish and chip shops in Britain in the 1860s, drive-through restaurants were first popularized in the 1950s in the United States. The term fast food was recognized in a dictionary by Merriam–Webster in 1951, according to the National Institutes of Health, fast foods are quick alternatives to home-cooked meals. They are also high in saturated fat, sugar, salt, Eating too much fast food has been linked to, among other things, colorectal cancer, obesity and high cholesterol. The traditional family dinner is increasingly being replaced by the consumption of takeaway, as a result, the time invested on food preparation is getting lower and lower, with an average couple in the United States spending 47 minutes and 19 seconds per day on food preparation in 2013. The concept of ready-cooked food for sale is closely connected with urban development, homes in emerging cities often lacked adequate space or proper food preparation accouterments. Additionally, procuring cooking fuel could cost as much as purchased produce, frying foods in vats of searing oil proved as dangerous as it was expensive, and homeowners feared that a rogue cooking fire might easily conflagrate an entire neighborhood. Thus, urbanites were encouraged to purchase pre-prepared meats or starches, such as bread or noodles, in Ancient Rome, cities had street stands - a large counter with a receptacle in the middle from which food or drink would have been served. It was during post-WWII American economic boom that Americans began to more and buy more as the economy boomed. As a result of this new desire to have it all, coupled with the strides made by women while the men were away, Eating out, which had previously been considered a luxury, became a common occurrence, and then a necessity. Workers, and working families, needed quick service and inexpensive food for lunch and dinner. This need is what drove the phenomenal success of the early fast food giants, Fast food became an easy option for a busy family, as is the case for many families today. In the mornings, bread soaked in wine was eaten as a snack and cooked vegetables and stews later in popina. In Asia, 12th century Chinese scarfed down fried dough, soups and their Baghdadi contemporaries supplemented home-cooked meals with processed legumes, purchased starches, and even ready-to-eat meats. As in Roman cities during antiquity, many of these establishments catered to those who did not have means to cook their own food, unlike richer town dwellers, many often could not afford housing with kitchen facilities and thus relied on fast food. Travelers, as well, such as en route to a holy site, were among the customers
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Red meat
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Commonly, especially in gastronomy, red meat or dark meat is red when raw and dark in color when cooked, in contrast to white meat, which is pale in color before and after cooking. This definition only refers to flesh from mammals or fowl, in nutritional science, red meat is defined as any meat that has more myoglobin than white meat, white meat being defined as non-dark meat from chicken, or fish. Some meat, such as pork, is red meat using the nutritional definition, according to the USDA, all meats obtained from mammals are red meats because they contain more myoglobin than fish or white meat from chicken. The culinary definition has many rules and exceptions, generally meat from mammals and meat from hunting excluding fish and insects are considered red meat. Although poultry is usually considered white, duck and goose are red, for some animals the culinary definition of red meat differs by cut, and sometimes by the age of the animal is when it was slaughtered. Pork is considered red if the animal is adult, but white if young, the same applies to young lamb and veal. Game is sometimes put in a separate category altogether, Pork is considered white under the culinary definition, but red in nutritional studies. The National Pork Board has positioned it as Pork, the Other White Meat, profiting from the ambiguity to suggest that pork has the nutritional properties of white meat, which is considered more healthful. Red meat contains large amounts of iron, creatine, minerals such as zinc and phosphorus, red meat is a source of lipoic acid. Red meat contains small amounts of vitamin D, the liver contains much higher quantities than other parts of the animal. In 2011, the USDA launched MyPlate, which didnt distinguish between kinds of meat, but did recommend eating at least 8 oz of fish each week. In 2011, the Harvard School of Public Health launched the Healthy Eating Plate because of the inadequacies of the USDAs recommendations. The Healthy Eating Plate encourages consumers to limit red meat and avoid processed meat and its website says, Eating a lot of red meat and processed meat has been linked to increased risk of heart disease, diabetes, and colon cancer. So it’s best to avoid processed meat, and to limit red meat to no more than twice a week. Switching to fish, chicken, nuts, or beans in place of red meat and processed meat can improve cholesterol levels and can lower the risk of heart disease and diabetes. Red meat is not a product, its health effects can vary based on fat content, processing. Processed red meat is linked to mortality, mainly due to cardiovascular diseases. There is some evidence too that the consumption of unprocessed red meat may have health effects in humans
39.
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
40.
Poultry farming
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Poultry farming is the process of raising domesticated birds such as chickens, ducks, turkeys and geese for the purpose of farming meat or eggs for food. Poultry are farmed in great numbers with chickens being the most numerous, more than 50 billion chickens are raised annually as a source of food, for both their meat and their eggs. Chickens raised for eggs are called layers while chickens raised for meat are often called broilers. In the US, the organization overseeing poultry production is the Food. In the UK, the organisation is the Department for Environment, Food. According to the researchers and scientists, 74% of the poultry meat. One alternative to intensive poultry farming is free-range farming using lower stocking densities, Poultry producers routinely use nationally approved medications, such as antibiotics, in feed or drinking water, to treat disease or to prevent disease outbreaks. Some FDA-approved medications are also approved for improved feed utilization, commercial hens usually begin laying eggs at 16–20 weeks of age, although production gradually declines soon after from approximately 25 weeks of age. In some countries, hens are force moulted to re-invigorate egg-laying, Environmental conditions are often automatically controlled in egg-laying systems. Some commercial breeds of hen can produce over 300 eggs a year, in the UK, the Department for Environment, Food and Rural Affairs states that a free-range chicken must have day-time access to open-air runs during at least half of its life. Unlike in the United States, this also applies to free-range egg laying hens. Free-range farming of egg-laying hens is increasing its share of the market, defra figures indicate that 45% of eggs produced in the UK throughout 2010 were free-range, 5% were produced in barn systems and 50% from cages. This compares with 41% being free-range in 2009, suitable land requires adequate drainage to minimise worms and coccidial oocysts, suitable protection from prevailing winds, good ventilation, access and protection from predators. Excess heat, cold or damp can have an effect on the animals. Free-range farmers have less control than farmers using cages in what food their chickens eat, in some farms, the manure from free-range poultry can be used to benefit crops. The benefits of free-range poultry farming for laying hens include opportunities for natural behaviours such as pecking, scratching, foraging, both intensive and free-range farming have animal welfare concerns. Cannibalism, feather pecking and vent pecking can be common, prompting farmers to use beak trimming as a preventative measure. Diseases can be common and the animals are vulnerable to predators, barn systems have been found to have the worst bird welfare
41.
Developed country
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Which criteria are to be used and which countries can be classified as being developed are subjects of debate. Developed countries have post-industrial economies, meaning the sector provides more wealth than the industrial sector. They are contrasted with developing countries, which are in the process of industrialization, or undeveloped countries, which are pre-industrial and almost entirely agrarian. As of 2015, advanced economies comprise 60. 8% of global GDP based on values and 42. 9% of global GDP based on purchasing-power parity according to the International Monetary Fund. In 2015, the ten largest advanced economies by GDP in both nominal and PPP terms were Australia, Canada, France, Germany, Italy, Japan, South Korea, Spain, the United Kingdom, and the United States. The term industrialized country may be ambiguous, as industrialization is an ongoing process that is hard to define. The first industrialized country was the United Kingdom, followed by Belgium, later it spread further to Germany, United States, France and other Western European countries. According to some such as Jeffrey Sachs, however, the current divide between the developed and developing world is largely a phenomenon of the 20th century. Economic criteria have tended to dominate discussions, one such criterion is income per capita, countries with high gross domestic product per capita would thus be described as developed countries. Another economic criterion is industrialization, countries in which the tertiary and quaternary sectors of industry dominate would thus be described as developed. More recently another measure, the Human Development Index, which combines an economic measure, national income, with other measures, indices for life expectancy and this criterion would define developed countries as those with a very high rating. According to the United Nations Statistics Division, There is no established convention for the designation of developed, the UN HDI is a statistical measure that gauges a countrys level of human development. While there is a correlation between having a high HDI score and a prosperous economy, the UN points out that the HDI accounts for more than income or productivity. Unlike GDP per capita or per capita income, the HDI takes into account how income is turned into education and health opportunities, since 1990, Norway, Japan, Canada and Iceland have had the highest HDI score. The top 47 countries have scores ranging from 0.793 in Barbados to 0.955 in Norway, many countries listed by IMF or CIA as advanced, possess an HDI over 0.788. Many countries possessing an HDI of 0.788 and over are also listed by IMF or CIA as advanced, thus, many advanced economies are characterized by an HDI score of 0.9 or higher. Since April 2016, the IMF classifies Macau as an advanced economy, the latest index was released on 14 December 2015 and covers the period up to 2014. The following are the 49 countries in the top quartile - having an HDI above 0.8, = Increase = No increase or decrease = Decrease The number in parentheses represents the number of ranks the country has climbed relative to the ranking in 2014 report
Cookbook: Chicken 
Media: Chicken
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