Question

Put the following 5 steps of the phototransduction cascade in order:

I. The retinal goes from 11-cis to all trans, changes conformation of retinal and rhodopsin.
II. Sodium channels close without cGMP bound, rod hyperpolarizes, rod inactivated.
III. Light hits retinal in the rhodopsin (rod opsin).
IV. Transducin will break from rhodopsin, and the alpha subunit binds to Phosphodiesterase (PDE).
V. PDE converts cGMP->GMP.

(A) III > I > IV > V > II
(B) III > V > IV > I > II
(C) II > V > IV > I > III
(D) II > I > IV > V > III

Answer 1

The correct order for the phototransduction cascade is: Light activates rhodopsin, retinal changes conformation, transducin and PDE are activated, cGMP is converted to GMP, and sodium channels close leading to hyperpolarization of the rod cell (option A: III > I > IV > V > II).

Step-by-step explanation:

The process of phototransduction refers to the conversion of light into a neural signal in the retina, and it involves a cascade of biochemical steps. The correct sequence for the steps of the phototransduction cascade is as follows:

1. Light hits retinal in the rhodopsin (rod opsin).
2. The retinal goes from 11-cis to all trans, changes conformation of retinal and rhodopsin.
3. Transducin will break from rhodopsin, and the alpha subunit binds to Phosphodiesterase (PDE).
4. PDE converts cGMP to GMP.
5. Sodium channels close without cGMP bound, rod hyperpolarizes, rod inactivated This sequence is represented by option (A): III > I > IV > V > II, which correctly outlines the order of events from the impact of light on the retinal to the subsequent hyperpolarization of the rod cell.