The highly light-sensitive photopigment in rods is
(A) rhodopsin,
(B) rhodopsin,
(C) chloralabe,
(D) cyanolabe.
The correct answer and explanation is:
The correct answer is (A) rhodopsin.
Rhodopsin is the photopigment found in the rods of the retina, responsible for vision in low-light conditions. Rod cells are specialized for detecting dim light and are highly sensitive to light, making them essential for night vision. When light hits rhodopsin, it undergoes a chemical change that triggers a series of events inside the rod cell, ultimately leading to the transmission of visual signals to the brain. This process is called phototransduction.
Rhodopsin is a complex protein composed of two main components: opsin, a protein, and retinal, a light-absorbing molecule derived from vitamin A. When light strikes the retinal component of rhodopsin, it causes the molecule to change shape. This change in shape activates opsin, which then initiates a cascade of reactions inside the cell, resulting in the hyperpolarization of the rod cell and the transmission of an electrical signal to the brain.
The importance of rhodopsin lies in its ability to respond to even very low levels of light. Rods, unlike cones (which are responsible for color vision and function in bright light), do not distinguish color but are extremely sensitive to light intensity. This makes rhodopsin critical for vision in dim environments, like at night or in low-light settings.
The other options, such as chlorolabe and cyanolabe, refer to different photopigments found in cones (responsible for color vision), not rods. Rhodopsin, being a highly efficient light-sensitive molecule, allows rods to operate effectively under conditions of low illumination, where color differentiation is not necessary.