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Vitamins are substances that play an essential part in animal metabolic processes, but which the animals cannot synthesise. In their absence the animal develops certain deficiency diseases or other abnormal conditions. Vitamins are chemicals other than proteins, carbohydrates, fats and mineral salts that are essential constituents of the food of animals. Although certain animals can synthesise certain vitamins and all animals needing vitamin D can manufacture it from ergosterol in the presence of u.v. light, the precise mechanism of action of many vitamins is still poorly understood. Small amounts of vitamins are essential for the regulation of all bodily processes. With the exception of vitamin D, the human body cannot make its own vitamins, and some cannot be stored. Vitamins must therefore be obtained from a food on a daily basis. A person's diet must provide all the necessary vitamins.
Vitamin B12, cyanocobalamine, helps protect nerves and is involved in the formation of red blood cells in thee bone marrow. Vitamin B12 is also concerned in the biosynthesis of methyl groups of choline and methionine. The vitamin deficiency is often due to failure to absorb B12 from the stomach and can be alleviated by giving mg doses with extracts of hog's stomach which contains the intrinsic anti-pernicious anaemia factor (a mucoprotein) which promotes absorption.
Vitamin B12 is produced by the growth of certain micro-organisms and also occurs in the liver. Vitamin B12 has been prepared synthetically.
The structure of Vitamin B12 Vitamin B12 consists of : a monovalent cobalt metal at the center , surrounded by a porphyrin-like structure of tetrapyrrole rings , bound to the metal center is a cyano group and a 5',6'-dimethylbenzimidazolyl nucleotide which is linked to the tetrapyrrole rings via a phosphate sugar linkage .
Update by Karl Harrison
(Molecule of the Month for February 1997 )