<Tr> <Th> Pronunciation </Th> <Td> UK: / ˈvɪtəmɪn, ˈvaɪ - / US: / ˈvaɪtəmɪn / </Td> </Tr> <Tr> <Td_colspan="2"> In Wikidata </Td> </Tr> <P> A vitamin is an organic molecule (or related set of molecules) which is an essential micronutrient--that is, a substance which an organism needs in small quantities for the proper functioning of its metabolism but cannot synthesize, either at all or in sufficient quantities, and therefore must obtain through its diet . The term vitamin does not include the three other essential nutrients: essential mineral (nutrient) s, essential fatty acids, and essential amino acids . Some substances can be synthesized by a certain organism, but not by another: that substance is not a vitamin in the first instance, but it is in the second . Most vitamins are not single molecules, but groups of related molecules called vitamers . Vitamins are classified by their biological / chemical activity, not their structure . The thirteen vitamins required by human metabolism are: vitamin A (retinols and carotenoids), vitamin B (thiamine), vitamin B (riboflavin), vitamin B (niacin), vitamin B (pantothenic acid), vitamin B (pyridoxine), vitamin B (biotin), vitamin B (folic acid or folate), vitamin B (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones). </P> <P> Vitamins have diverse biochemical functions . Some forms of vitamin A function as regulators of cell and tissue growth and differentiation . The B complex vitamins function as enzyme cofactors (coenzymes) or the precursors for them . Vitamin D has a hormone - like function as a regulator of mineral metabolism, and is anti-proliferative . Vitamin E (and sometimes vitamin C), functions as an antioxidant . Both deficient and excess intake of a vitamin can potentially cause clinically significant illness; although excess intake of a water - soluble vitamin is least likely to do so . All vitamins were discovered (identified) between 1913 and 1948 . </P>

What is the scientific name of vitamin b3