Explain Transport and Utilization of Vitamin A?
The efficacy of the intestines to facilitate absorption and utilization of retinoid s and carotenoids depends upon the cellular uptake of these compounds into the intestinal mucosal cell, bioavailability or passage of the molecules beyond the intestinal mucosa into the body with the potential for storage or use in tissues and bioconversion i.e., production of active retinoid from provitmin A carotenoids. Inside the intestinal cells, ß-carotene is cleaved by a cytosolic enzyme 15-15' oxygenase to form retinaldehyde, which is then reduced by the microtonal enzyme retinal reductase to retinal. Thus, the ultimate product formed in the intestines is retinol, which is then re-esterifies with long chain fatty acids by intra cellular retinol-binding proteins (CRBP) and packed into chylomicron containing cholesterol esters, phospholipids, triacylglycerol etc. What happens to this chylomicrons.