Vitamin K (Molecule of the Month for February 1997)
Structures of Vitamins
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 K is needed for effective blood clotting. A deficiency is rare due to bacteria synthesis within the body. Vitamin K is an accessory factor needed chickens, ducks, and geese, the absence of which is characterized by hemorrhages due to a failure of the blood to clot properly. The factor is associated in some way with prothrombin, and may be part of the prothrombin molecule.
Vitamin K1 is from alfalfa oil, it is 2-mehtl-3-phytyl-1,4-naphthoquinone. The term vitamin K2 was applied to 2-methyl-3-difarnesyl-1,4-naphthoquinone, isolated from putrefied fish meal. It now includes a group of related natural compounds - menaquinones, differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in electron transport mechanism and oxdative phosphorylation.
Good sources of Vitamin K are most vegetables. It is fat-soluble and found in the liver fats, vegetables and to a lesser extent cereals. It is stable to heat and light and destroyed by alkalis.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for February 1997 )