HLTB11H3 Lecture Notes - Lecture 9: Retinol, Visual Phototransduction, Beta-Carotene
22 Apr 2016
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Vitamin a: source: liver, eggs, diary, yellow/orange/red fruits/veggies, role: visual pigment (night vision) regulation of gene expression / cell differentiation. Night blindness; xerophthalmia; increase susceptibility to infection: toxicity: preformed vit a highly toxic (liver damage, birth defect) Acute: nausea, vomiting, headache, dizziness, blurred vision, muscle uncoordination (artic explorers polarbears liver) Chronic: weight loss, muscle/joint pain, born abnormalities, fracture, dry lips, skin rash. Teratogen: causes birth defect; pregnant woman should not eat liver: form: carotenoids. Beta carotene is converted to retinol; conversion is inefficient: not all beta-carotene is absorbed, not all beta-carotene is converted to retinol. Beta-carotene circulates in the blood: acts as antioxidant, reduces risk of lung cancer, visual cycle: night blindness. Light strike the visual pigment rhodopsin (opsin and retinal) If low vitamin a status, regeneration of rhodopsin is delay. Until it is reformed light cannot be perceived: retinoic acid binds to a receptor in the nucleus binds to a.
