Which photopigment is found in the rods of the eye and is needed for night vision?

• A. Rhodopsin
• B. Iodopsin
• C. Photopsin
• D. Macropsin

Answer: (A)

Rods handle night vision, and the photopigment they use is rhodopsin. In darkness, rhodopsin is inactive; when light hits it, retinal changes shape and activates the opsin protein, triggering a cascade that lowers cGMP levels, closes sodium channels, and hyperpolarizes the rod. This signaling is highly sensitive to low light, allowing you to detect dim environments, though it won’t convey color well. Cones, on the other hand, use different pigments (iodopsin and other cone photopigments) that support color and sharp vision in bright light. Macropsin isn’t a standard human photopigment. So the pigment in rods needed for night vision is rhodopsin.