BPK 110 Lecture Notes - Vitamin A Deficiency, Retinoid, Xerophthalmia
11 Aug 2012
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Document Summary
Pro-vitamin form, converted to retinoid form by body as needed. Retinal forms part of the molecule called rhodopsin. Rhodopsin is found in the cells of the retina (back of eye) Important for converting a light stimulus to an electrical signal which allows brain to interpret visual info. After entering the eye, light strikes the visual pigment rhodopsin, which is formed by combining retinal with the protein pepsin. Light causes the retinal molecule to change from a bent to a straight configuration. A nerve signal is sent to the brain, telling that there is light, and retinal is released from opsin. Some retinal returns to its original configuration and binds to opsin to being the cycle again. When vitamin a status is normal, vitamin a from the blood replaces any retinal lost from the cycle. When vitamin a is deficient, not enough vitamin a is available in the blood, and the regeneration of rhodopsin is delayed.
