What are the roles of vitamin A in human body?

Vitamin A refers to all isoprenoid compounds from animal products with the biological activity of all-trans-retinol. Vitamin A activity depends on the presence of one, non-hydroxylated beta-ionone ring in the provitamin A structure.

There are three active forms of vitamin A in the body known as retinoids – retinol (an alcohol), retinal (an aldehyde), and retinoic acid (an acid). Carotenoid (plant pigments) can also be converted to vitamin A by the liver.

Vitamin A (retinol) functions in reproduction, growth, the maintenance of skin and mucous membranes and the visual process.

Epithelial cells (those cells present in the lining of body cavities and in the skin and glands) require vitamin A.

Vitamin A is normally transported in the blood linked to a specific protein, retinol binding protein (RBP). Specific proteins on cell surfaces and within cells are also involved with intracellular transport of the vitamin.

The role of vitamin A in maintenance of eye health and the visual cycle is quite well understood. Retinoic acid is required for normal differentiation of the cornea, conjunctival membranes and photoreceptor rod and cone cells of the retina.

Vitamin A is fat soluble and is primarily stored in the liver, where RBP is synthesized. In a well nourished person, vitamin A stores are generally sufficient to last many months on a vitamins A-deficient diet before signs of deficiency appear.
What are the roles of vitamin A in human body?

Related Posts Plugin for WordPress, Blogger...

Popular Posts

  • Heat exchangers are designed for a rated or nominal condition. The most commonly used heat exchanger is the shell and tube type. It is the ‘workhorse’ of i...
  • Antioxidants have been described as “substance that, when present at low concentrations compared with those of an oxidizable substrate, significantly retar...
  • Of the many foods obtained from the land, humans tend to prefer animal foods, mainly beef, pork, poultry and mutton as well as their by-products e.g. chees...