Question

What happens when light falls on a photoreceptor cell?
(i) Retinol dissociates from opsin.
(ii) The structure of opsin changes.
(iii) The membrane permeability changes.

• A. i and ii
• B. ii and iii
• C. iii and iv
• D. i and iv

Answer 1

The correct option is B ii and iii

The photosensitive compound (rhodopsin) in the
human eyes is composed of opsin (a protein) and retinal (an aldehyde form of vitamin A). Light induces the dissociation of the retinal from opsin resulting in changes in the structure of the opsin. This causes membrane permeability changes. As a result, action potentials are generated, which are then transmitted to the brain.
Retinol is vitamin A and is not a part of rhodopsin.