Biochemistry

Vitamin А 2 differs from vitamin Aj in that it has an additional double bond between the 3 rd and 4 th carbohydrate atoms of the six-membered ring. И 3 С \ /C H 3 ch 3 CH 3 H,C xCx C-CH=CH-C=CH-CH=CH-C=CH-CH 2 OH 2 1 II НСч xC-CH, CH Dehydroretinol (Vitamin A 2 ) Retinol consists of a mixture of cyclic unsaturated alcohols with a large number of conjugated double bonds. These are yellow crystalline bodies, readily soluble in fats, gasoline, ether, chloroform, acetone and other substances. In the absence of oxygen, retinol is stable even at 100 °C. It is rapidly oxidized and destroyed in air, especially in an acidic environment. Ultraviolet rays also contribute to this. Vitamin A can be stored in the liver in the form of more stable esters with acetic or palmitic acids. A retinal (aldehyde) is also formed from retinol when oxidized in the body, which also has vitamin activity. Biological role. One of the important functions of vitamin A is its participation in the formation of the complex protein rhodopsin - visual purpura in the retina, which provides adaptation to different light intensities. Rhodopsin consists of opsin protein and an aldehyde form of vitamin A- retinal. 262