1.
Species
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In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas
2.
Maize
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Maize, also known as corn, is a large grain plant first domesticated by indigenous peoples in Mexico about 10,000 years ago. The six major types of corn are dent corn, flint corn, pod corn, popcorn, flour corn, the leafy stalk of the plant produces separate pollen and ovuliferous inflorescences or ears, which are fruits, yielding kernels or seeds. Maize kernels are used in cooking as a starch. Most historians believe maize was domesticated in the Tehuacan Valley of Mexico, recent research modified this view somewhat, scholars now indicate the adjacent Balsas River Valley of south-central Mexico as the center of domestication. The Olmec and Mayans cultivated maize in numerous varieties throughout Mesoamerica, cooked and its believed that beginning about 2500 BC, the crop spread through much of the Americas. The region developed a network based on surplus and varieties of maize crops. Nevertheless, recent data indicates that the spread of maize took place even earlier, according to Piperno, A large corpus of data indicates that it was dispersed into lower Central America by 7600 BP and had moved into the inter-Andean valleys of Colombia between 7000 and 6000 BP. Since then, even earlier dates have been published, the study also demonstrated that the oldest surviving maize types are those of the Mexican highlands. Later, maize spread from this region over the Americas along two major paths and this is consistent with a model based on the archaeological record suggesting that maize diversified in the highlands of Mexico before spreading to the lowlands. Before they were domesticated, maize plants only grew small,25 millimetres long corn cobs, Maize is the most widely grown grain crop throughout the Americas, with 361 million metric tons grown in the United States in 2014. Approximately 40% of the crop—130 million tons—is used for corn ethanol, genetically modified maize made up 85% of the maize planted in the United States in 2009. After the arrival of Europeans in 1492, Spanish settlers consumed maize and explorers and traders carried it back to Europe, Spanish settlers far preferred wheat bread to maize, cassava, or potatoes. Maize flour could not be substituted for wheat for bread, since in Christian belief only wheat could undergo transubstantiation. At another level, Spaniards worried that by eating indigenous foods, which they did not consider nutritious, that not only would they weaken, despite these worries, Spaniards did consume maize and archeological evidence from Florida sites indicate they cultivated it as well. Maize spread to the rest of the world because of its ability to grow in diverse climates and it was cultivated in Spain just a few decades after Columbuss voyages and then spread to Italy, West Africa and elsewhere. The word maize derives from the Spanish form of the indigenous Taíno word for the plant and it is known by other names around the world. The word corn outside North America, Australia, and New Zealand refers to any cereal crop, in the United States, Canada, Australia, and New Zealand, corn primarily means maize, this usage started as a shortening of Indian corn. Indian corn primarily means maize, but can more specifically to multicolored flint corn used for decoration
3.
Sugar
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Sugar is the generic name for sweet, soluble carbohydrates, many of which are used in food. There are various types of derived from different sources. Simple sugars are called monosaccharides and include glucose, fructose, the table sugar or granulated sugar most customarily used as food is sucrose, a disaccharide of glucose and fructose. Sugar is used in prepared foods and it is added to some foods, in the body, sucrose is hydrolysed into the simple sugars fructose and glucose. Other disaccharides include maltose from malted grain, and lactose from milk, longer chains of sugars are called oligosaccharides or polysaccharides. Some other chemical substances, such as glycerol may also have a sweet taste, low-calorie food substitutes for sugar, described as artificial sweeteners, include aspartame and sucralose, a chlorinated derivative of sucrose. Sugars are found in the tissues of most plants and are present in sufficient concentrations for efficient commercial extraction in sugarcane, the world production of sugar in 2011 was about 168 million tonnes. The average person consumes about 24 kilograms of sugar each year, equivalent to over 260 food calories per person, since the latter part of the twentieth century, it has been questioned whether a diet high in sugars, especially refined sugars, is good for human health. Sugar has been linked to obesity, and suspected of, or fully implicated as a cause in the occurrence of diabetes, cardiovascular disease, dementia, macular degeneration, the etymology reflects the spread of the commodity. The English word sugar ultimately originates from the Sanskrit शर्करा, via Arabic سكر as granular or candied sugar, the contemporary Italian word is zucchero, whereas the Spanish and Portuguese words, azúcar and açúcar, respectively, have kept a trace of the Arabic definite article. The Old French word is zuchre and the contemporary French, sucre, the earliest Greek word attested is σάκχαρις. The English word jaggery, a brown sugar made from date palm sap or sugarcane juice, has a similar etymological origin – Portuguese jagara from the Sanskrit शर्करा. Sugar has been produced in the Indian subcontinent since ancient times and it was not plentiful or cheap in early times and honey was more often used for sweetening in most parts of the world. Originally, people chewed raw sugarcane to extract its sweetness, sugarcane was a native of tropical South Asia and Southeast Asia. Different species seem to have originated from different locations with Saccharum barberi originating in India and S. edule, one of the earliest historical references to sugarcane is in Chinese manuscripts dating back to 8th century BC that state that the use of sugarcane originated in India. Sugar was found in Europe by the 1st century AD, but only as an imported medicine and it is a kind of honey found in cane, white as gum, and it crunches between the teeth. It comes in lumps the size of a hazelnut, sugar is used only for medical purposes. Sugar remained relatively unimportant until the Indians discovered methods of turning sugarcane juice into granulated crystals that were easier to store, crystallized sugar was discovered by the time of the Imperial Guptas, around the 5th century AD
4.
Dominance (genetics)
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Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus. The first allele is dominant and the allele is recessive. For genes on an autosome, the alleles and their traits are autosomal dominant or autosomal recessive. Dominance is a key concept in Mendelian inheritance and classical genetics, often the dominant allele codes for a functional protein whereas the recessive allele does not. A classic example of dominance is the inheritance of seed shape in peas, peas may be round, associated with allele R or wrinkled, associated with allele r. In this case, three combinations of alleles are possible, RR, Rr, and rr, the RR individuals have round peas and the rr individuals have wrinkled peas. In Rr individuals the R allele masks the presence of the r allele, thus, allele R is dominant to allele r, and allele r is recessive to allele R. This use of upper case letters for dominant alleles and lower case ones for recessive alleles is a widely followed convention, more generally, where a gene exists in two allelic versions, three combinations of alleles are possible, AA, Aa, and aa. Dominance is not inherent to either an allele or its phenotype and it is a relationship between two alleles of a gene and their associated phenotypes, one allele can be dominant over a second allele, recessive to a third allele, and codominant to a fourth. Also, an allele may be dominant for an aspect of phenotype. Dominance differs from epistasis, a relationship in which an allele of one gene affects the expression of another allele at a different gene, the concept of dominance was introduced by Gregor Johann Mendel. Though Mendel, The Father of Genetics, first used the term in the 1860s, when bred separately, the plants always produced the same phenotypes, generation after generation. However, when lines with different phenotypes were crossed, one, Mendel did not use the terms gene, allele, phenotype, genotype, homozygote, and heterozygote, all of which were introduced later. He did introduce the notation of capital and lowercase letters for dominant and recessive alleles, respectively, most animals and some plants have paired chromosomes, and are described as diploid. They have two versions of each chromosome, one contributed by the mothers ovum, and the other by the sperm, known as gametes, described as haploid. Each chromosome of a pair is structurally similar to the other. The DNA in each chromosome functions as a series of genes that influence various traits. Thus, each also has a corresponding homologue, which may exist in different versions called alleles
5.
Mutation
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In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements. Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements, mutations may or may not produce discernible changes in the observable characteristics of an organism. Mutations play a part in normal and abnormal biological processes including, evolution, cancer, and the development of the immune system. The genomes of RNA viruses are based on RNA rather than DNA, the RNA viral genome can be double stranded or single stranded. In some of these viruses replication occurs quickly and there are no mechanisms to check the genome for accuracy and this error-prone process often results in mutations. Mutation can result in different types of change in sequences. Mutations in genes can either have no effect, alter the product of a gene, mutations can also occur in nongenic regions. Mutations can involve the duplication of large sections of DNA, usually through genetic recombination and these duplications are a major source of raw material for evolving new genes, with tens to hundreds of genes duplicated in animal genomes every million years. Most genes belong to larger families of shared ancestry, known as homology. Here, protein domains act as modules, each with a particular and independent function, that can be mixed together to produce genes encoding new proteins with novel properties. For example, the eye uses four genes to make structures that sense light. Another advantage of duplicating a gene is that this increases engineering redundancy, other types of mutation occasionally create new genes from previously noncoding DNA. Changes in chromosome number may involve even larger mutations, where segments of the DNA within chromosomes break and then rearrange. For example, in the Homininae, two fused to produce human chromosome 2, this fusion did not occur in the lineage of the other apes. Sequences of DNA that can move about the genome, such as transposons, make up a fraction of the genetic material of plants and animals. For example, more than a million copies of the Alu sequence are present in the genome. Another effect of these mobile DNA sequences is that when they move within a genome, they can mutate or delete existing genes, nonlethal mutations accumulate within the gene pool and increase the amount of genetic variation. The abundance of some changes within the gene pool can be reduced by natural selection, while other more favorable mutations may accumulate
6.
Starch
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Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as an energy store and it is the most common carbohydrate in human diets and is contained in large amounts in staple foods such as potatoes, wheat, maize, rice, and cassava. Pure starch is a white, tasteless and odorless powder that is insoluble in water or alcohol. It consists of two types of molecules, the linear and helical amylose and the branched amylopectin, depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. Glycogen, the store of animals, is a more branched version of amylopectin. In industry, starch is converted into sugars, for example by malting and it is processed to produce many of the sugars used in processed foods. Dissolving starch in water gives wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process, starch can be applied to parts of some garments before ironing, to stiffen them. The word starch is from a Germanic root with the strong, stiff. Amylum for starch is from the Greek αμυλον, amylon which means not ground at a mill, the root amyl is used in biochemistry for several compounds related to starch. Starch grains from the rhizomes of Typha as flour have been identified from grinding stones in Europe dating back to 30,000 years ago, starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago. Pure extracted wheat starch paste was used in Ancient Egypt possibly to glue papyrus, the extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79. Romans used it also in cosmetic creams, to powder the hair, persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in production in China. In addition to starchy plants consumed directly,66 million tonnes of starch were being produced per year world-wide by 2008. In the EU this was around 8.5 million tonnes, with around 40% being used for applications and 60% for food uses. Most green plants use starch as their energy store, an exception is the family Asteraceae, where starch is replaced by the fructan inulin. In photosynthesis, plants use light energy to produce glucose from carbon dioxide, the glucose is used to make cellulose fibers, the structural component of the plant, or is stored in the form of starch granules, in amyloplasts
7.
Vegetable
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In everyday usage, a vegetable is any part of a plant that is consumed by humans as food as part of a meal. The term vegetable is somewhat arbitrary, and largely defined through culinary and it normally excludes other food derived from plants such as fruits, nuts, and cereal grains, but includes seeds such as pulses. The original meaning of the vegetable, still used in biology, was to describe all types of plant, as in the terms vegetable kingdom. At first, plants which grew locally would have been cultivated, nowadays, most vegetables are grown all over the world as climate permits, and crops may be cultivated in protected environments in less suitable locations. China is the largest producer of vegetables and global trade in agricultural products allows consumers to purchase vegetables grown in faraway countries, the scale of production varies from subsistence farmers supplying the needs of their family for food, to agribusinesses with vast acreages of single-product crops. Depending on the type of vegetable concerned, harvesting the crop is followed by grading, storing, processing, and marketing. Vegetables can be either raw or cooked and play an important role in human nutrition, being mostly low in fat and carbohydrates. Many nutritionists encourage people to consume plenty of fruit and vegetables, the word vegetable was first recorded in English in the early 15th century. It comes from Old French, and was applied to all plants. It derives from Medieval Latin vegetabilis growing, flourishing, a change from a Late Latin meaning to be enlivening, quickening. The meaning of vegetable as a plant grown for food was not established until the 18th century, in 1767, the word was specifically used to mean a plant cultivated for food, an edible herb or root. The year 1955 saw the first use of the shortened, slang term veggie, the broadest definition is the words use adjectivally to mean matter of plant origin to distinguish it from animal, meaning matter of animal origin. More specifically, a vegetable may be defined as any plant, part of which is used for food, a secondary meaning then being the edible part of such a plant. A more precise definition is any plant part consumed for food that is not a fruit or seed, falling outside these definitions are edible fungi and edible seaweed which, although not parts of plants, are often treated as vegetables. In everyday language, the fruit and vegetable are mutually exclusive. Fruit has a precise meaning, being a part that developed from the ovary of a flowering plant. This is considerably different from the words culinary meaning, while peaches, plums, and oranges are fruit in both senses, many items commonly called vegetables, such as eggplants, bell peppers, and tomatoes, are botanically fruits. The question of whether the tomato is a fruit or a vegetable found its way into the United States Supreme Court in 1893
8.
Cereal
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A cereal is any grass cultivated for the edible components of its grain, composed of the endosperm, germ, and bran. Cereal grains are grown in quantities and provide more food energy worldwide than any other type of crop and are therefore staple crops. Edible grains from plant families, such as buckwheat, quinoa. In their natural form, cereals are a source of vitamins, minerals, carbohydrates, fats, oils. When refined by the removal of the bran and germ, the endosperm is mostly carbohydrate. In some developing nations, grain in the form of rice, wheat, millet, in developed nations, cereal consumption is moderate and varied but still substantial. The word cereal is derived from Ceres, the Roman goddess of harvest, agriculture allowed for the support of an increased population, leading to larger societies and eventually the development of cities. It also created the need for organization of political power, as decisions had to be made regarding labor and harvest allocation and access rights to water. Agriculture bred immobility, as populations settled down for long periods of time, early Neolithic villages show evidence of the development of processing grain. The Levant is the ancient home of the ancestors of wheat, barley and peas, there is evidence of the cultivation of figs in the Jordan Valley as long as 11,300 years ago, and cereal production in Syria approximately 9,000 years ago. During the same period, farmers in China began to farm rice and millet, using man-made floods, fiber crops were domesticated as early as food crops, with China domesticating hemp, cotton being developed independently in Africa and South America, and Western Asia domesticating flax. The first cereal grains were domesticated by early primitive humans, about 8,000 years ago, they were domesticated by ancient farming communities in the Fertile Crescent region. Emmer wheat, einkorn wheat, and barley were three of the so-called Neolithic founder crops in the development of agriculture, around the same time, millets and rices were starting to become domesticated in East Asia. Sorghum and millets were also being domesticated in sub-Saharan West Africa, while each individual species has its own peculiarities, the cultivation of all cereal crops is similar. Most are annual plants, consequently one planting yields one harvest, wheat, rye, triticale, oats, barley, and spelt are the cool-season cereals. These are hardy plants grow well in moderate weather and cease to grow in hot weather. The warm-season cereals are tender and prefer hot weather, barley and rye are the hardiest cereals, able to overwinter in the subarctic and Siberia. Many cool-season cereals are grown in the tropics, however, some are only grown in cooler highlands, where it may be possible to grow multiple crops per year
9.
Canning
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Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a shelf life ranging from one to five years. A freeze-dried canned product, such as canned dried lentils, could last as long as 30 years in an edible state. In 1974, samples of canned food from the wreck of the Bertrand, although appearance, smell and vitamin content had deteriorated, there was no trace of microbial growth and the 109-year-old food was determined to be still safe to eat. The larger armies of the period required increased and regular supplies of quality food, limited food availability was among the factors limiting military campaigns to the summer and autumn months. In 1809, Nicolas Appert, a French confectioner and brewer, observed that food cooked inside a jar did not spoil unless the seals leaked, Appert was awarded the prize in 1810 by Count Montelivert, a French minister of the interior. The reason for lack of spoilage was unknown at the time, unfortunately for Appert, the factory which he had built with his prize money was razed in 1814 by Allied soldiers when they entered France. Following the end of the Napoleonic Wars, the process was gradually employed in other European countries. Durand did not pursue food canning himself, selling his patent in 1811 to Bryan Donkin and John Hall, Bryan Donkin developed the process of packaging food in sealed airtight cans, made of tinned wrought iron. Initially, the process was slow and labour-intensive, as each large can had to be hand-made. The main market for the food at this stage was the British Army, by 1817 Donkin recorded that he had sold £3000 worth of canned meat in six months. In 1824 Sir William Edward Parry took canned beef and pea soup with him on his voyage to the Arctic in HMS Fury, in 1829, Admiral Sir James Ross also took canned food to the Arctic, as did Sir John Franklin in 1845. Some of his stores were found by the expedition led by Captain Leopold McLintock in 1857. One of these cans was opened in 1939, and was edible and nutritious, throughout the mid-19th century, canned food became a status symbol amongst middle-class households in Europe, being something of a frivolous novelty. Increasing mechanization of the process, coupled with a huge increase in urban populations across Europe. Demand for canned food greatly increased during wars, urban populations in Victorian Britain demanded ever-increasing quantities of cheap, varied, quality food that they could keep at home without having to go shopping daily. In response, companies such as Underwood, Nestlé, Heinz, in particular, Crosse and Blackwell took over the concern of Donkin Hall and Gamble. Shortages of canned food in the British Army in 1917 led to the government issuing cigarettes and amphetamines to soldiers to suppress their appetites, after the war, companies that had supplied military canned food improved the quality of their goods for civilian sale
10.
Dent corn
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Dent corn also known as yellow dent corn, Reids yellow dent corn, white dent corn, or field corn, is a variety of maize or corn with a high soft starch content. It received its name because of the small indentation at the crown of each kernel on an ear of corn. It is a variety developed by northern Illinois farmer James L. Reid, most of todays hybrid corn varieties and cultivars are derived from it. This variety won a prize at the 1893 Worlds Fair, most of the corn grown in the United States today is yellow dent corn or a closely related variety derived from it. Dent corn is the variety used in manufacturing as the base ingredient for cornmeal flour, corn chips, tortillas. Starch derived from this high-starch content variety is turned into plastics, as well as fructose which is used as a sweetener in many processed foods, Zea mays var. indentata, synonym Zea indentata Sturtev. was identified and published by American agronomist and botanist Edward Lewis Sturtevant. Dent corn is a fast-growing, vertically erect, short-lived annual plant, the leaves of Zea mays alternate with broad, sword-shaped leaf blades, parallel veins with a prominent mid-rib, and small ligules. The plant has an adventitious, dense, fibrous root system that develops aerial roots at nodes near the soil surface, the flowers of Zea mays are monoecious, and are born in separate parts of the plant. The female flowers, or ears, are an inflorescence that develops from axillary bud apices several nodes below the stem apex, male flowers, or tassels, develop from the stem apex. Anthers on the tassel dehisce and release pollen, which is dispersed by the wind, ears consist of a corncob, or rachis, with rows of sessile spikelets bearing kernels, or caryopses, and tightly enveloped by several layers of ear leaves commonly called husks. The kernels vary from variety to variety, and what distinguishes Zea mays var. indentata apart other varieties of Zea mays is the small indentation that develops at the crown of each kernel. Comparatively, flint corn has a harder-textured, more rounded kernel that may display a slight depression, dent corn is typically cultivated as a row crop grown commercially for grain and fodder. Cultivars developed for cultivation are either single- or double-cross hybrids bred for special growing areas. According to the U. S. Department of Agricultures Federal Grain Inspection Service and these hybrids are categorized by the colour of the kernels—either yellow or white. Yellow dent corn is produced primarily for animal feed and industrial uses such as ethanol, FGIS identifies that white food corn hybrids are dent corn. Dependent on their content, some yellow dent corn hybrids are grown. Corn production in the United States
11.
Flint corn
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Flint corn is a variant of maize, the same species as common corn. Because each kernel has an outer layer to protect the soft endosperm, it is likened to being hard as flint. With less soft starch than dent corn, flint corn does not have the dents in each kernel from which dent corn gets its name. This is one of the three types of corn cultivated by Native Americans, both in New England and across the northern tier, including by such as the Pawnee on the Great Plains. Archeologists have found evidence of corn cultivation by the Pawnee. Cultivation of corn occurred hundreds of years earlier among the Mississippian culture people, whose civilization arose based on population density, because flint corn has a very low water content, it is more resistant to freezing than other vegetables. It was the only Vermont crop to survive New Englands infamous Year Without a Summer of 1816, the coloration of flint corn is often different from white and yellow dent corns, many of which were bred later. Like the Linnaeus variant of maize, any kernel may contain the yellow pigment zeaxanthin, popcorn is considered a variant of this type. It has a hard, slightly translucent kernel, flint corn is also the type of corn preferred for making hominy, a staple food in the Americas since pre-Columbian times. The flint corn cultivars that have large proportions of kernels with hues outside the range are primarily used ornamentally, notably as part of Thanksgiving decorations in the United States. They are often called either ornamental corn or Indian corn, although each of those names has other meanings as well and these varieties can also be popped and eaten as pop corn
12.
Popcorn
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Popcorn is a type of corn that expands from the kernel and puffs up when heated. Popcorn is able to pop like amaranth grain, sorghum, quinoa, when heated, pressure builds within the kernel, and a small explosion is the end result. Some strains of corn are now cultivated specifically as popping corns, there are various techniques for popping corn. Along with prepackaged popcorn, which is intended to be prepared in a microwave oven. These methods require the use of minimally processed popping corn, a larger-scale, commercial popcorn machine, which resembled a modern movie theater popcorn machine on a cart with large bicycle style wheels, was invented by Charles Cretors in the late 19th century. Unpopped popcorn is considered nonperishable and will last indefinitely if stored in ideal conditions, depending on how it is prepared and cooked, some consider popcorn to be a health food, while others caution against it for a variety of reasons. Popcorn can also have applications, ranging from holiday decorations to packaging materials. Corn was first domesticated in Mexico 9,000 years ago, archaeologists have discovered that people have known about popcorn for thousands of years. In Mexico, for example, they’ve found remnants of popcorn that dates to around 3600 BC, popping of the kernels was achieved manually through the 19th century, being sold on the east coast of the USA under names such as Pearls or Nonpareil. The term popped corn first appeared in John Russell Bartlett’s 1848 Dictionary of Americanisms, Popcorn is an ingredient in Cracker Jack, and in the early years of the product, it was popped by hand. Popcorns accessibility increased rapidly in the 1890s with Charles Cretors invention of the popcorn maker, Cretors, a Chicago candy store owner, created a number of steam powered machines for roasting nuts, and applied the technology to the corn kernels. By the turn of the century, Cretors had created and deployed street carts equipped with steam powered popcorn makers, during the Great Depression, popcorn was fairly inexpensive at 5–10 cents a bag and became popular. Thus, while businesses failed, the popcorn business thrived and became a source of income for many struggling farmers, including the Redenbacher family. During World War II, sugar rations diminished candy production, the snack was popular at theaters, much to the initial displeasure of many of the theater owners, who thought it distracted from the films. Their minds eventually changed, however, and in 1938 a Midwestern theater owner named Glen W. Dickson installed popcorn machines in the lobbies of his theaters, the venture was a financial success, and the trend soon spread. In 1970, Orville Redenbachers namesake brand of popcorn was launched, in 1981, General Mills received the first patent for a microwave popcorn bag, with popcorn consumption seeing a sharp increase by tens of thousands of pounds in the years following. At least six localities claim to be the Popcorn Capital of the World, Ridgway, Illinois, Valparaiso, Indiana, Van Buren, Indiana, Schaller, Iowa, Marion, Ohio, and North Loup, Nebraska. According to the USDA, corn used for production is specifically planted for this purpose, most is grown in Nebraska and Indiana
13.
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
14.
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
15.
Dietary fiber
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Dietary fiber or roughage is the indigestible portion of food derived from plants. It has two components, Soluble fiber, which dissolves in water, is readily fermented in the colon into gases and physiologically active byproducts. It delays gastric emptying which in turn can cause a feeling of fullness. Insoluble fiber, which does not dissolve in water, is inert and provides bulking, or it can be prebiotic. Bulking fibers absorb water as they move through the digestive system, Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed. Some types of soluble fiber absorb water to become a gelatinous, viscous substance which is fermented by bacteria in the digestive tract, some types of insoluble fiber have bulking action and are not fermented. Lignin, a major dietary insoluble fiber source, may alter the rate, other types of insoluble fiber, notably resistant starch, are fully fermented. A novel position has been adopted by the US Department of Agriculture to include functional fibers as isolated fiber sources that may be included in the diet, the term fiber is something of a misnomer, since many types of so-called dietary fiber are not actually fibrous. Food sources of fiber are often divided according to whether they provide soluble or insoluble fiber. Plant foods contain both types of fiber in varying degrees, according to the plants characteristics, a disadvantage of a diet high in fiber is the potential for significant intestinal gas production and bloating. Originally, fiber was defined to be the components of plants that resist human digestive enzymes, the definition was later changed to also include resistant starch, along with inulin and other oligosaccharides. Official definition of dietary fiber differs a little among different institutions, Dietary fibers are found in fruits, vegetables, the exact amount of fiber contained in the food can be seen in the following table of expected fiber in USDA food groups/subgroups Dietary fiber is found in plants. While all plants contain some fiber, plants with high concentrations are generally the most practical source. Fiber-rich plants can be eaten directly, or, alternatively, they can be used to make supplements and fiber-rich processed foods. The Academy of Nutrition and Dietetics, formerly the American Dietetic Association, some plants contain significant amounts of soluble and insoluble fiber. For example, plums and prunes have a thick skin covering a juicy pulp, the skin is a source of insoluble fiber, whereas soluble fiber is in the pulp. Grapes also contain an amount of fiber. The root of the plant, or glucomannan, produces results similar to fiber
16.
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
17.
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
18.
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
19.
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
20.
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
21.
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
22.
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
23.
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
24.
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
25.
Phenylalanine
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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
26.
Tyrosine
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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
27.
Valine
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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
28.
Histidine
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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
29.
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
30.
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
31.
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
32.
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
33.
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
34.
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
35.
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
36.
Folate
–
Folic acid, another form of which is known as folate, is one of the B vitamins. The recommended daily level of folate is 400 micrograms from foods or dietary supplements. Folic acid is used to treat anemia caused by folic acid deficiency and it is also used as a supplement by women during pregnancy to prevent neural tube defects in the baby. Low levels in early pregnancy are believed to be the cause of more than half of babies born with neural tube defects, more than 50 countries use fortification of certain foods with folic acid as a measure to decrease the rate of NTDs in the population. Long term supplementation is also associated with reductions in the risk of stroke. It may be taken by mouth or by injection, there are no common side effects. It is not known whether high doses over a period of time are of concern. There are concerns that large amounts of folic acid might hide vitamin B12 deficiency, folic acid is essential for the body to make DNA, RNA, and metabolise amino acids which are required for cell division. As humans cannot make folic acid, it is required from the diet, not consuming enough folate can lead to folate deficiency. This may result in a type of anemia in which low numbers of red blood cells occur. Symptoms may include feeling tired, heart palpitations, shortness of breath, open sores on the tongue, deficiency in children may develop within a month of poor dietary intake. In adults normal total body folate is between 10, 000–30,000 micrograms with blood levels of greater than 7 nmol/L, folic acid was discovered between 1931 and 1943. It is on the World Health Organizations List of Essential Medicines, the wholesale cost of supplements in the developing world is between 0.001 and 0.005 USD per dose as of 2014. The term folic is from the Latin word folium, which means leaf, folates occur naturally in many foods especially dark green leafy vegetables and liver. Other names include vitamin B9, vitamin Bc, vitamin M, folacin, folic acid intake during pregnancy has been linked to a lessened risk of neural tube defects. Likewise, a meta-analysis of folic acid supplementation during pregnancy reported a 28% lower risk of congenital heart defects. The United States Preventive Services Task Force recommends folic acid supplementation for all able to become pregnant. Prenatal supplementation did not appear to reduce the risk of pre-term births, and there does not appear to be a correlation between maternal folic acid supplementation and an increased risk for asthma in the child
37.
Vitamin C
–
Vitamin C, also known as ascorbic acid and L-ascorbic acid, is a vitamin found in food and used as a dietary supplement. As a supplement it is used to treat and prevent scurvy, evidence does not support use in the general population for the prevention of the common cold. It may be taken by mouth or by injection, large doses may cause gastrointestinal discomfort, headache, trouble sleeping, and flushing of the skin. Normal doses are safe during pregnancy, Vitamin C is an essential nutrient involved in the repair of tissue. Foods that contain vitamin C include citrus fruit, tomatoes, Vitamin C was discovered in 1912, isolated in 1928, and first made in 1933. It is on the World Health Organizations List of Essential Medicines, Vitamin C is available as a generic medication and over the counter. In 2015, the wholesale cost in the world was about 0.003 to 0.007 USD per tablet. In some countries, ascorbic acid may be added to such as breakfast cereal. A2012 Cochrane review found no effect of vitamin C supplementation on overall mortality, although rare in modern times, scurvy and its associated destabilization of collagen, connective tissue, and bone can be prevented by adequate vitamin C intake. A2014 review found that, Currently, the use of high-dose IV vitamin C cannot be recommended outside of a clinical trial, a 2013 Cochrane review found no evidence that vitamin C supplementation reduces the risk of lung cancer in healthy or high risk people. A2014 meta-analysis found that vitamin C intake might protect against lung cancer risk, a second meta-analysis found no effect on the risk of prostate cancer. Two meta-analyses evaluated the effect of vitamin C supplementation on the risk of colorectal cancer, one found a weak association between vitamin C consumption and reduced risk, and the other found no effect of supplementation. A2013 meta-analysis found no evidence that vitamin C supplementation reduces the risk of myocardial infarction, stroke, cardiovascular mortality, however, a second analysis found an inverse relationship between circulating vitamin C levels or dietary vitamin C and the risk of stroke. A meta-analysis of 44 clinical trials has shown a significant positive effect of vitamin C on endothelial function when taken at doses greater than 500 mg per day. The researchers noted that the effect of vitamin C supplementation appeared to be dependent on health status, a 2010 review found no role for vitamin C supplementation in the treatment of rheumatoid arthritis. Studies examining the effects of vitamin C intake on the risk of Alzheimers disease have reached conflicting conclusions, maintaining a healthy dietary intake is probably more important than supplementation for achieving any potential benefit. Vitamin C supplementation above the RDA has been used in trials to study a potential effect on preventing and slowing the progression of age-related cataract, however, no significant effects were found from the research. Vitamin Cs effect on the cold has been extensively researched
38.
Human iron metabolism
–
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
39.
Magnesium in biology
–
Magnesium is an essential element in biological systems. Magnesium occurs typically as the Mg2+ ion and it is an essential mineral nutrient for life and is present in every cell type in every organism. For example, ATP, the source of energy in cells. What is called ATP is often actually Mg-ATP, as such, magnesium plays a role in the stability of all polyphosphate compounds in the cells, including those associated with the synthesis of DNA and RNA. Over 300 enzymes require the presence of ions for their catalytic action, including all enzymes utilizing or synthesizing ATP. In plants, magnesium is necessary for synthesis of chlorophyll and photosynthesis, a balance of magnesium is vital to the well-being of all organisms. Magnesium is a relatively abundant ion in Earths crust and mantle and is highly bioavailable in the hydrosphere and this availability, in combination with a useful and very unusual chemistry, may have led to its utilization in evolution as an ion for signaling, enzyme activation, and catalysis. However, the nature of ionic magnesium has also led to a major challenge in the use of the ion in biological systems. Biological membranes are impermeable to magnesium, so transport proteins must facilitate the flow of magnesium, chlorophyll in plants converts water to oxygen as O2. Hemoglobin in vertebrate animals transports oxygen as O2 in the blood, chlorophyll is very similar to hemoglobin, except magnesium is at the center of the chlorophyll molecule and iron is at the center of the hemoglobin molecule, with other variations. This process keeps living cells on earth alive and produces levels of CO2 and O2 in our atmosphere that has changed with industrialization. Acute deficiency is rare, and is common as a drug side-effect than from low food intake per se. The most common symptom of excess oral magnesium intake is diarrhea, since the kidneys of adult humans excrete excess magnesium efficiently, oral magnesium poisoning in adults with normal renal function is very rare. Infants, which have less ability to excrete excess magnesium even when healthy, should not be given magnesium supplements, pharmaceutical preparations with magnesium are used to treat conditions including magnesium deficiency and hypomagnesemia, as well as eclampsia. Such preparations are usually in the form of sulfate or chloride when given parenterally. Magnesium is absorbed with reasonable efficiency by the body from any soluble magnesium salt, Magnesium is similarly absorbed from Epsom salts, although the sulfate in these salts adds to their laxative effect at higher doses. The Food and Nutrition Board of the U. S, institute of Medicine updated Estimated Average Requirements and Recommended Dietary Allowances for magnesium in 1997. The current EARs for magnesium for women and men ages 31 and up are 265 mg/day and 350 mg/day, the RDAs are 320 and 420 mg/day
40.
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
