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How is retinal related to vitamin A?
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Photoreception
The mammalian eye has a cornea and a lens and functions as a dioptric system, in which light rays are refracted to focus on the retina.
Retinal is a vital component of the visual process, and its relationship to vitamin A is fundamental to human sight. Specifically, retinal is a substance derived from the oxidation of vitamin A.1
In the context of biology and photoreception, this relationship functions as follows:
- Visual Pigment Formation: Vitamin A is converted into retinaldehyde (retinal), which then combines with a protein called opsin to form rhodopsin, a light-sensitive pigment found in the retina of the eye.31
- The Photochemical Process: When light strikes the retina, it triggers a change in the shape of the retinal molecule (photoisomerization), which leads to the bleaching of rhodopsin and the eventual splitting of retinal from opsin. This chemical change is the trigger that initiates the electrical signals sent to the optic nerve.21
- Regeneration and Deficiency: Within the retina, these changes are reversible; in the dark, retinal and opsin rejoin to regenerate rhodopsin. Because retinal is derived from vitamin A, a deficiency in the vitamin prevents the proper maintenance of rhodopsin, leading to night blindness and other ocular disturbances.123