Definition of "photopigment" []

• Any pigment that is unstable in the presence of light; used especially of the chromophore pigments in the rod cells and cone cells of the eye (noun)

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• "Invertebrates have rhabodomeric cells that use a special version of the photopigment called r-opsin, and activate cells by a particular pathway called a phospholipase-C cascade."
• "The ability to see the world as humans do, he says, ‘requires an additional sensor—or photopigment—and the nervous system being able to compare the signals.’"
• "For example, he would claim that a photopigment without any linkers or down stream signalling molecules would be useless, and unselectable by natural selection."