Question

Photopigments of the human eye are composed of a protein called
(A) Melanin
(B) Retinal
(C) Opsin
(D) Myosin
(E) Troponin

Answer 1

Hint: Photopigments are the unstable pigments that undergo a chemical change when they absorb light. Commonly these pigments refer to photoreceptors Proteins of the retina.

Complete answer:
Option A- Melanin
Melanin is the pigment responsible for darkness in the skin. Hair, skin, and eye color of human beings and animals totally depend on the type and amount of melanin produced.

Option B- Retinal
Also known as retinal pigmented epithelium (RPE). It is the pigmented layer outside the retina which helps to nourish the retinal cells. It is an aldehyde of vitamin A and found bounding to photopigments in the retina.

Option C-Opsin
Opsin is the light-sensitive proteins found in the photoreceptor cells of the retina that are cons and rods. Cones contain rhodopsin, porphyrin and cyanopsia whereas in Rods contain rhodopsin.

Option D-Myosin
Myosin is a motor protein that plays a crucial role in muscle contraction and also helps in other motility processes.

Option E-Troponin
Troponin is a protein of muscle fibers. It is a complex of three proteins (troponin C, troponin I, and troponin T) that are essential for the contraction of skeletal muscles, cardiac muscles but not for the smooth muscles.

Thus the correct option is (C) Opsin.

Note: Opsins are G protein-coupled receptors that are present in the photoreceptors of the retina which initiate vision upon activation by light. Cone opsin is present in the cone photoreceptor cells and responsible for the photopic vision on the other hand rhodopsin is responsible for the scotopic vision.