Question

Which option correctly describes the response of a photoreceptor to light?
A) Light activation leads to a decrease in sodium influx
B) Light activation leads to an increase in potassium influx
C) Light activation leads to a decrease in potassium efflux
D) Light activation leads to an increase in sodium influx
E) Light activation leads to an increase in sodium efflux

Answer 1

Answer:

The correct answer will be option A.

Explanation:

Photoreceptors are the cells present in the retina of the eye which respond to the light. Each photoreceptor is made up of two molecule - a protein (opsin) and a chromophore (retinal).

When light falls on the eye, the chromophore-retinal absorbs the photons which cause configurational changes in the structure of retinal as the double bond present between 11th and 12th carbon is flipped due to which cis bonds are changed to all-trans bonds. This configurational change leads to the closure of sodium (Na+) channels in the membrane which stops the influx of the sodium.

Therefore, option-A is the correct answer.