Photopigments are composed of opsin and which molecule?

Study for the IMAT Biology Exam with focused multiple-choice questions. Use hints and explanations to enhance your preparation. Get ready for your exam success!

Photopigments in the retina are built from an opsin protein bound to a light-absorbing molecule called retinal. Retinal, a derivative of vitamin A, attaches to opsin to form the functional pigment; when light is absorbed, retinal changes shape (11-cis to all-trans), triggering a cascade that starts the visual signal. The other options don’t fit because opsin is the protein part, melanin is a pigment for protection rather than the chromophore of photopigments, and hemoglobin is the oxygen-carrying molecule in blood.