Figure 1. Pathway the rhodopsin follows to reach meterhosopsin II
When a photon of light is absorbed by the choromophore, rhodopsin changes is shape to accomodate the change in the chromophore from 11-cis retinal to all trans retinal. Rhodopsin changes to metarhdopsin II through a series of intermediate as seen below. 11-cis retinal is found in rhodopsin, sometimes refered to as photorhodopsin, while all trans retinal is found in metarhodopsin II.
Figure 1. Pathway the rhodopsin follows to reach meterhosopsin II
Once the meterhodopsin conformation is reached, rhodopsin activates the phototransduction cascade and visual excitation is reached. The metarhdopsin II conformation breaks down to all trans retinal + opsin in a process called bleaching. The retinal is then release from the opsin which is embedded in the membrane. Regeneration of the molecule is occurs spontaeously when the another 11-cis retinal from the surroundings bind to opsin. The released all trans retinal is reduced to trans retinol by a membrane bound dehydrogenase and NADPH. The retinol migrents to the outter rod segments and retinal pigment epithelium. There the retinol is esterified. The trans retinol is taken up by an enzyme highly specific for trans retinol and converts it back to 11-is retinal.