Rod cells use retinol from the bloodstream to
A) transport visual messages to the brain.
B) replace the retinal lost during bleaching.
C) regenerate the protein iodopsin.
D) stabilize free radicals in the rod cell membrane.

Question

Quizplus · Accepted Answer

Retinol (vitamin A) is used in the visual cycle to regenerate the light-sensitive pigment rhodopsin in rod cells. When light is absorbed by rhodopsin, retinal (derived from vitamin A) dissociates from it, leading to bleaching of the pigment. Retinol from the bloodstream then enters the rod cells to regenerate the retinal and reform rhodopsin, thus allowing for continued vision in low light situations. Therefore, choice B is the correct answer.

Rod Cells Use Retinol from the Bloodstream to