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Definition of RHODOPSIN
: a red photosensitive pigment in the retinal rods of the eye of most vertebrates that is important in vision in dim light —called also visual purple
Origin of RHODOPSIN
International Scientific Vocabulary rhod- + Greek opsis sight, vision + International Scientific Vocabulary 1-in — more at optic
First Known Use: 1886
Medical Definition of RHODOPSIN
: a red photosensitive pigment in the retinal rods of marine fishes and most higher vertebrates that is important in vision in dim light, is quickly bleached by light to a mixture of opsin and retinal, and is regenerated in the dark—called also visual purple
Light-sensitive, purple-red organic pigment contained in the rod cells of the retina that allows the eye to see in black and white in dim light. It is composed of opsin, a protein, linked to retinal, a conjugated molecule (seeconjugation) formed from vitamin A. Photons of light that enter the eye are absorbed by retinal and cause it to change its configuration, starting a biochemical chain of events that ends with impulses being sent along the optic nerve to the brain. In bright light, to protect rod cells from overstimulation, rhodopsin breaks down into retinal and opsin, both of which are colourless. In dim light or darkness the process is reversed (dark adaptation), and purple-red rhodopsin is reformed. Similar light-sensitive compounds made of retinal and other opsin proteins are the pigments in the retina's cone cells responsible for colour vision in bright light.