Vitamin K

The different vitamins K are fat-soluble, heat-stable and resistant to reducing agents, however these are light sensitive. These vitamins are destroyed by light, alkalies, strong acids and various oxidizing agents. There are some of vitamins K: K1, K2 and menadione. VK1 has been obtained from alfalfa leaves, vK2 has been obtained from Bacillus brevis (it is also named farnoquinone).

Sources and absorption Important sources of vitamins K group are alfalfa, cabbage, cauliflower, tomatoes, spinach and other green vegetables. Among the animal sources are fish, liver, cheese and egg-yolk. The intestinal flora of microorganism can also synthesize these vitamins.

Absorption of these vitamins occurs in the intestine and it requires bile-salts. Presence of bile-salts is essential. In obstruction of biliary tract, the absorption of vK is markedly reduced. In such cases, bile-salt preparation must be orally administrated to promote vitamin K absorption. Although, vitamin K are stored but the site of storage is not known deficiency.

Functions: vK promote the biosynthesis of prothrombin in the liver tissue. Prothrombin in an important protein which after converting into thrombin acquires enzymic activity and converts fibrinogen into fibrin (blood ) – thus, vK facilitates the process of blood coagulation. Therefor deficiency of this vitamin delayes in coagulation of blood. This vitamin can pass from mother to fetus with considerable difficulty.

Since, vK possess quinoid structure which can be readily reduced and deoxidized. The possibility of its involvement in biological oxidation can not ruled out. Current view is that vK in the form of coenzyme Q forms the normal electron carrier and is also believed to help in the oxidative phosphorylation process.

It has been indicated that vK acts as an induser for RNA formation. These RNA molecules help in the biosynthesis of prothrombin and possibly other proteins in the clotting process.

Requirement: the daily norm do not established, appr. 2mg/day

Carbohydrates metabolism. digestion and absorption of carbohydrates. intermediate metabolism of carbohydrates

<== попередня сторінка	\|	наступна сторінка ==>
Deficiency diseases	\|	The role of carbohydrates

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