<P> Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol , retinal , retinoic acid , and several provitamin A carotenoids ( most notably beta - carotene ) . Vitamin A has multiple functions : it is important for growth and development , for the maintenance of the immune system and good vision . Vitamin A is needed by the retina of the eye in the form of retinal , which combines with protein opsin to form rhodopsin , the light - absorbing molecule necessary for both low - light ( scotopic vision ) and color vision . Vitamin A also functions in a very different role as retinoic acid ( an irreversibly oxidized form of retinol ) , which is an important hormone - like growth factor for epithelial and other cells . </P>
<P> Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol , retinal , retinoic acid , and several provitamin A carotenoids ( most notably beta - carotene ) . Vitamin A has multiple functions : it is important for growth and development , for the maintenance of the immune system and good vision . Vitamin A is needed by the retina of the eye in the form of retinal , which combines with protein opsin to form rhodopsin , the light - absorbing molecule necessary for both low - light ( scotopic vision ) and color vision . Vitamin A also functions in a very different role as retinoic acid ( an irreversibly oxidized form of retinol ) , which is an important hormone - like growth factor for epithelial and other cells . </P>
the retinoid that has the most important physiological role in the human body is
the retinoid that has the most important physiological role in the human body is
Vitamin A
Vitamin A