BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The two main forms of vitamin A in the human diet are preformed vitamin A (retinol, retinyl esters), and provitamin A carotenoids such as beta-carotene that are converted to retinol. Preformed vitamin A comes from animal products, fortified foods, and vitamin supplements. Carotenoids are found naturally in plant foods.

Detailed explanation-2: -Retinol: Preformed retinol is an active form of vitamin A. It is found in animal liver, whole milk, and some fortified foods.

Detailed explanation-3: -Preformed vitamin A is found in foods from animal sources, including dairy products, eggs, fish, and organ meats [1, 2]. Provitamin A carotenoids are plant pigments that the body converts into vitamin A in the intestine [1, 3].

Detailed explanation-4: -Beta-carotene is the pigment that gives carrots, sweet potatoes, and other yellow vegetables their characteristic coloring. This conjugated polyene also serves as a precursor that can be enzymatically converted into vitamin A in most animals and man.

Detailed explanation-5: -Vitamin A comes from two sources. One group, called retinoids, comes from animal sources and includes retinol. The other group, called carotenoids, comes from plants and includes beta-carotene. The body converts beta-carotene to vitamin A.