Which of the Following is the Primary Second Messenger in G-Protein

Question

Which of the following is the primary second messenger in G-protein coupled post-synaptic cells?
A) NO
B) CO
C) cAMP
D) GABA
E) ATP

Accepted Answer

cAMP (cyclic adenosine monophosphate) is the primary second messenger in G-protein coupled post-synaptic cells. It is synthesized from ATP by the enzyme adenylyl cyclase, which is activated by the G protein. cAMP then activates protein kinase A (PKA), leading to changes in cellular activity. NO (nitric oxide) and CO (carbon monoxide) are also second messengers, but not primarily associated with G-protein signaling. GABA (gamma-aminobutyric acid) and ATP (adenosine triphosphate) are neurotransmitters, not second messengers.