The visual cycle is a biochemical mechanism wherein rhodopsin, a photosensitive pigment in rod cells composed of opsin and 11-cis retinal (a Vitamin A derivative), undergoes reversible structural changes upon photon absorption. The core principle involves the photo-isomerization of 11-cis retinal to all-trans retinal within rhodopsin, triggering ion channel cascades for nerve impulse generation; subsequent thermal reconstitution restores dark-adapted sensitivity via enzymatic regeneration in the retina and liver. This process defines the physiological basis for scotopic (low-light) vision adaptation and establishes the biochemical dependency between Vitamin A levels and synaptic transmission fidelity in the visual system.
The visual cycle is a biochemical mechanism wherein rhodopsin, a photosensitive pigment in rod cells composed of opsin and 11-cis retinal (a Vitamin A derivative), undergoes reversible structural cha…