360 



ANIMAL BIOCHEMISTRY 



thoquinones with the general formula shown or may be converted to 

 such quinones in the body. The two natural vitamins have been iso- 



O 



r^^^^N 



-CH3 



-R 



O 



lated from alfalfa and from fish meal, and their respective structures 

 are as follows: 



O 



V^ 



-CH3 



CH3 



GH3 



-CH2GH=GGH2— [GHaCHsGHGHaJs— H 



O 



vitamin Ki 



-GH3 ™' 



^[GHoGH=GGH2l6— H 



vitamin K2 



Two other forms are widely used clinically under various trade names. 

 Both are extremely effective. When a water-soluble form is required 



O O 



-CH. 



GH3 



NH 



in cases of difficulties in the absorption ol lipidcs, the hydrcKhloridc 

 of the last compound is used. 



Vitamin K has a single known function. It is required for the 

 formation of one of the components of the prothrombin system essen- 

 tial for the clotting of blood when the circulatory system is damaged. 

 The mechanism by which this function is performed is quite unknown. 



This factor is rather widely distributed and is abundant in green 

 leaves. It is extensively synthesized by the intestinal flora of the 



