Question

Which one of the following is not a second messenger in hormone action?

• A. cGMP
• B. Calcium
• C. Sodium
• D. cAMP

Answer 1

Answer: (C)

Second messengers are the organic molecules and sometimes the metal ions, act as intracellular signals, whose production or release usually amplifies a signal such as a hormone, received at the cell surface.
Sodium $(Na)$ is not a second messenger in hormone action.
Cyclic Adenosine Monophosphate (cAMP) was the first "second messenger" to be discovered.
In addition to cyclic AMP, Cyclic Guanosine Monophosphate (cGMP) functions as a second messenger in certain cases.
Calcium ions $\left(C{a}^{2+}\right)$ also act as second messenger in phospholipase $C-C{a}^{+}$second messenger system.