Biochemistry · Vitamins & Minerals

Which form of vitamin A serves as the chromophore that binds opsin to form rhodopsin in rod photoreceptor cells?

A 11-cis-retinal ✓
B Retinol
C Retinoic acid
D Beta-carotene

Correct answer: A. 11-cis-retinal

Explanation

11-cis-retinal is the aldehyde form of vitamin C that binds opsin to form rhodopsin. Photon absorption isomerizes it to all-trans-retinal, triggering the visual cascade. Retinol is the transport and storage form. Retinoic acid regulates gene transcription. Beta-carotene is a dietary precursor cleaved to retinal.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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