Fat-Soluble Vitamins; Vitamin A
Vitamin A Vitamin A; most essential vitamin Vitamin A refers to the performed retinoids and provitamin A carotenoids that can be converted to vitamin A activity. Retinoids is a collective term for the biologically active forms of vitamin A. They are called performed vitamin A because, unlikely carotenoids, they do not need to be converted in the body to become biologically active. Retinoids exist in 3 forms; retinol, retinal and retinoic acid. The tail segment of the vitamin A structure terminates in 1 of these 3 chemical groups and determines the name or classification. To some extent, these can be interconverted . However, retinoic acid cannot be converted back to the other forms. the ability to interconvert forms helps maintain adequate amounts of each retinol form for its unique functions. Carotenoids are yellow-orange pigmented materials in fruits and vegetables, some of which are provitamins __that is, they can be converted into vitamin A. Of the 600 or more kno...