Final answer:
Opsin and retinal combine to form rhodopsin, a pigment essential for low-light vision found in the retina's rod cells. The Rhodopsin cycle perpetuates through biochemical changes induced by light, maintaining visual perception.
Step-by-step explanation:
The protein opsin and the molecule retinal combine to form the pigment found in rods called rhodopsin. Retinal exists as 11-cis-retinal before light exposure and upon photon interaction, it undergoes a process called photoisomerization, changing to all-trans-retinal. Rhodopsin is essential in the process of phototransduction, which takes place in the retina of the eye, enabling vision in low-light conditions.
During the Rhodopsin cycle, when light strikes the retina, rhodopsin splits into opsin and all-trans-retinal. Subsequently, all-trans-retinal is reduced to all-trans retinol, interacts with blood, isomerizes into cis-retinol, and then returns to the retina as cis-retinal. Finally, the cis-retinal rebinds with opsin, reforming rhodopsin and continuing the cycle of visual perception.