A vitamin is an organic compound as a nutrient needed in small quantities by an organism. In other words, is an organic chemical compound (or group of related compounds) is called a vitamin when
it can not be synthesized in sufficient quantities by an organism and must be obtained through diet. Thus, the term is conditional both on the circumstances and the individual organism. For example, ascorbic acid (vitamin C), a vitamin for humans, but not for most other animals, and biotin, and vitamin D is needed in the human diet only in certain circumstances. By convention, vitamin term does not include other essential nutrients such as dietary minerals, essential fatty acids or essential amino acids (which are needed in larger amounts than vitamins), does not include the many other nutrients that promote health, but otherwise required less often. Thirteen vitamins are generally recognized at present.
Vitamins are classified by their biological and chemical activity, not its structure. Thus, each "vitamin" refers to a series of CAV compounds all show the biological activity associated with a particular vitamin. As a set of chemicals are grouped in alphabetical order of vitamin "generic descriptor" title, as "vitamin A", including the compounds of the retina, retinol and carotenoids known four. CAV, by definition, can be converted to the active form of the vitamin in the body, and are often inter-convertible to another, too.
Vitamins are a variety of biochemical functions. Some are similar to hormones acting regulator of mineral metabolism (eg vitamin D), or the regulators and cell growth and differentiation of tissues (eg some forms of vitamin). Others act as antioxidants (eg vitamin E, vitamin C and, at times). Most of the vitamins (eg B complex vitamins) function as a starting material an enzyme co-factors that help the enzymes work as catalysts of metabolism. Here the role of vitamins may be closely related to enzymes as part of prosthetic groups: for example, biotin is part of enzymes involved in the production of fatty acids. Vitamins can also be less closely linked to the enzyme catalysts, coenzymes, removable molecules that function to carry chemical groups or electrons between molecules. For example, folic acid is transported in various forms of carbon group - methyl, formyl and methylene - in the cell.
Although these roles in assisting enzyme-substrate reactions are vitamins' best-known functions of vitamin others are equally important.
Until the mid 1930's, when the first commercial yeast extract and semi-synthetic vitamin C tablets were sold supplements, vitamins were obtained solely through food intake and changes in diet (eg may occur during a period of growth) can alter the types and amounts of vitamins ingested. Vitamins have been produced as commodity chemicals and widely available as inexpensive supplements semisynthetic or synthetic food sources of multivitamins from the mid 20th century.
Term vitamin is derived from "vitamin", a word set consisting of the Polish scientist Casimir Funk vital and amine, ie, amines of life, as was suggested in 1912 that organic food factors with micronutrients that prevents beriberi and perhaps other similar diseases dietary deficiency could be chemicals amines. This proved to be incorrect for the class of micronutrients, and the word is reduced to the vitamin.
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