Vitamin A is a fat soluble vitamin that is required for a number of bodily functions. This vitamin is needed to maintain good vision and a healthy immune system, as well as being essential for growth and development.
Vitamin A describes a group of compounds that include retinol, retinoic acid, retinal, and a number of provitamin A carotenoids such as beta-carotene. All types of vitamin A contain a beta-ionone ring with an isoprenoid chain attached which is referred to as the retinyl group. Both structures are required for vitamin activity.