Final answer:
The incorrect statement regarding vitamin A's role in vision is that retinal changes its shape from trans to cis when light strikes rhodopsin. In fact, it changes from cis to trans upon light absorption. The correct answer is Option C.
Step-by-step explanation:
Among the options presented, the statement that is NOT true regarding vitamin A's role in vision is: C. When light strikes rhodopsin, retinal changes its shape from trans to cis. The correct process that occurs is the opposite; retinal changes from a cis to a trans configuration upon light absorption.
Vitamin A is essential for vision, specifically for the formation and function of rhodopsin, a pigment found in the rod cells of the retina. A deficiency in vitamin A can lead to delays in the reformation of rhodopsin after it splits, which can result in night blindness. Rhodopsin consists of two parts: the protein opsin and the molecule retinal. Retinal, which is derived from vitamin A, is critical for the photoisomerization process that transduces light into neural signals.
When photons strike the retina, retinal absorbs the light and undergoes a change in shape from 11-cis-retinal to all-trans-retinal, the latter having a straight hydrocarbon chain. This change activates the rhodopsin and initiates a series of events that generate an electrical signal, which is sent to the brain to produce a visual image. It's the re-isomerization from trans to cis in the absence of light that readies the visual system for perceiving new light stimuli.
The correct answer to the student's question is Option C.