Question

Iodopsin occurs in
A. Iris
B. Rods
C. Cones
D. Lens

Answer 1

Hint: Iodopsin is a photosensitive violet coloured pigment. This pigment is formed by vitamin A.

Complete Answer:
Iris, Rods, Cones and Lens all are the parts of the eye. Eyes are the organ of sight. Eyes detect light and convert it in the form of electrical signals to the neurons.
1. Iris: Iris is the thin and annular structure found in the eyes of mammals, birds, humans, etc.
- Iris is responsible for controlling the diameter and size of the pupil.
- Thus it helps in regulating the amount of light reaching to the retina.
- Iris also determines the colour of the eye.

2. Rods: Rods are the type of photoreceptor cells that are present on the retina.
- These cells are responsible for the day light vision and night vision as they are sensitive to the light levels.
- These cells are concentrated in the outer areas of the retina.
 - Rods have little role in colour vision. Rod cells have the photopigment rhodopsin.

3. Cones: Cones are also the photoreceptor cells present on the retina of the eyes of vertebrates.
- They are responsible for the colour vision.
- The cone cells contain iodopsin as a violet coloured photopigment which is used in night vision.
- Cones cells are densely packed in the fovea centralis region of the retina.

4. Lens: The lens of the vertebrates have a transparent biconvex lens.
- The lenses help to refract light focused on the retina.
- It can change the focal length of the eye by changing its shape. The changing of focal length of eye of the lens is called as accommodation. The lens is also called aquila.

Therefore, we have seen in the above discussion that the Iodopsin occurs in cones.

Note: Accomodation is too important in order to see a clear image of an object as its distance varies. The far point of the human eye is defined as accommodation of the eye.