Question

This is a list of some of the steps in the process of seeing a flash of light. Put them in cause-and-effect order from first to last.

A. Photons pass through the ganglion and bipolar cells in the retina
B. Phosphodiesterases break down cyclic GMP
C. A photon is absorbed by a retinal molecule
D. The rod is hyperpolarized
E. Photons are refracted by the lens
F. Transducin molecules bind GTP
G. cGMP-gated Na⁺ channels close
H. Rhodopsin changes shape to its active conformation
I. Photons pass through the cornea
J. Transducin molecules activate phosphodiesterases

Answer 1

I,E,A,C,H, F,J,B,G,D

When we see the flash of light , the photons pass through the cornea and refracted by the lens.Then the photons pass through the bipolar and ganglion cells of the retina .A retinal molecule , rhodopsin absorbs a photon and changes its shape from 11-cis isomer to all trans- retinal .

This change activates a intracellular messenger, transducin which binds to GTP. Each transducin activates phosphodiesterase that hydrolyzes cyclic GMP ( guanosine monophosphate) . Availability of cyclic GMP become low which enable closure of sodium channels and make the membrane hyperpolarised.