Question

Pigment iodopsin is contained in
(A) Rod cells
(B) Cone cells
(C) Amacrine cells
(D) Horizontal cells

Answer 1

Hint:
Iodopsin pigments are found in one of the retinal cells. Retinal cells are present in the eyes. These cells are responsible for light vision. There are two types of photopigment cells i.e. rods and cones cells. Rods cells are responsible for dark or dim light vision whereas cones cells are responsible for light vision.

Complete answer:
Photoreceptor cells are pigmented cells present in the eye of humans. Two types of photoreceptor cells are present in eyes:
Rods: Rod cells are responsible for dim light vision. Rod cells are made up of rhodopsin protein. This rhodopsin protein is the derivative of vitamin A.
Cones: Cones cells are responsible for coloured visions. They are made up of iodopsin pigment.
Amacrine cells are interneurons in the retina. They are inhibitory neurons and found to be operated in the region of inner plexiform layer. Inner plexiform is the synaptic retinal layer in which bipolar cells and retinal ganglion cells form synapse. Iodopsin pigment is not found in amacrine cells. That’s why “option C” is incorrect.
Horizontal cells are the interconnecting neurons. They are found in the inner nuclear layer of the retina. Inner nuclear layer is made up of a closely packed arrangement of bipolar, horizontal, and amacrine cells. They increase via lateral inhibition in which it reduces the activity of neighboring neurons. Horizontal cells are not made up of iodopsin. That’s why “option D” is incorrect.
Iodopsin pigment is present in the cone cells.

Hence, the right answer is “cone cells”.

Note:
Iodopsin and rhodopsin are two different proteins. Don’t confuse between them. Iodopsins are found in cones cells. Whereas rhodopsin pigment is found in cones cells. Amacrine and horizontal cells are interneuron cells.