NUSCTX 10 Lecture Notes - Lecture 10: Visual Phototransduction, Retinol, Opsin
16 Dec 2015
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Vitamins a, d, e, and k: material substance required for other functions not fuel source that our body cannot make, must be obtained in the diet, require bile formed from cholesterol in liver and detergent like substance. Increases the risk of toxicity with high intakes. Vitamin a in the digestive tract: 3 vitamins. Converted one to another via enzymatic reactions; however, once you form retinoic acid, it doesn"t go back: preformed vitamin a; retinol-fatty acid (animal foods, beta carotene. Retinol retinal; can go back and forth. Retinal retinoic acid: vit a in the diet. Carrots: vit a and the visual cycle (double bonds) trans double bond cis double bond. Different shapes; cis is bent, trans is straight. 1) light enters eye, strikes the rhodopsin which has the protein opsin combined with retinal. Rhodopsin = membrane at back of eyeball binds to retinal. 2) light causes the retinal molecule to change from a bent to a straight.
