rhodopsin

Credit: Department of Ophthalmology, University of Utah

Also known as visual purple, a widely distributed pigment concerned with light sensitivity. Rhodopsin consists of a protein called opsin with a prosthetic group called retinal of which vitamin A is an essential precursor. Rhodopsin occurs in the rod cells of vertebrate retinas. It is chemically changed by the light, the change being the basis of how rods work as light-sensitive receptors. Rhodopsin increases in amount in the dark, raising the sensitivity of rods to faint light (the dark adaptation).

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