Question: 169: Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) :
FSH which interacts with membrane bound receptors does not enter the target cell.
Reason (R) :
Binding of FSH to its receptors generates second messenger (cyclic AMP) for its biochemical and physiological responses.
In the light of the above statements, choose the most appropriate answer from the options given below ;
(1) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(2) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(3) (A) is correct but (R) is not correct
(4) (A) is not correct but (R) is correct
Answer: Option (2)
Explanation:
Follicle Stimulating Hormone is a peptide hormone that acts by binding to specific membrane bound receptors on the target cell.
Since FSH is proteinaceous in nature, it cannot cross the lipid bilayer of the cell membrane and therefore does not enter the target cell.
Thus, Assertion (A) is correct.
When FSH binds to its membrane receptor, it activates a signal transduction pathway involving the formation of a second messenger, cyclic AMP.
Cyclic AMP then brings about the required biochemical and physiological responses inside the cell.
Hence, Reason (R) is also correct.
However, the generation of cyclic AMP explains how the signal is transmitted inside the cell,
not why FSH does not enter the cell.
Therefore, both (A) and (R) are correct, but (R) is not the correct explanation of (A).