BIOMOLECULES AND ENZYMES

Detailed explanation-1: -When the eye is exposed to light, the 11-cis-retinal component of rhodopsin is converted to all-trans-retinal, resulting in a fundamental change in the configuration of the rhodopsin molecule.

Detailed explanation-2: -Rhodopsin is the photosensitive pigment in the rod photoreceptor cell. Upon absorption of a photon, the covalently bound 11-cis retinal isomerizes to the all-trans form enabling rhodopsin to activate transducin, its G protein.

Detailed explanation-3: -All-trans-retinol is taken up from blood in the choroidal circulation through the basal membranes of RPE cells.

Detailed explanation-4: -All-trans-RAL is a major intermediate of the visual cycle. Continuous regeneration of the 11-cis chromophore from all-trans-RAL is essential for the renewal of light-sensitive visual pigments and determines photoreceptor survival in the vertebrate retina (4, 5).