Question

The hormone that activates the enzyme adenylate cyclase is:

• A. Epinephrine
• B. Insulin
• C. Estrogen
• D. Progesterone

Hint:

Epinephrine $\rightarrow$ GPCR $\rightarrow$ Adenylate Cyclase $\rightarrow$ cAMP.

Answer 1

The Correct Option is A

Step 1: Concept
Many hormones use the cyclic AMP (cAMP) second messenger system to relay signals into the cell.

Step 2: Meaning
Adenylate cyclase is the membrane-bound enzyme that converts ATP into cAMP.

Step 3: Analysis
Epinephrine (adrenaline) binds to $\beta$-adrenergic receptors, which are G-protein coupled receptors (GPCRs). This activation triggers a $G_{\alpha s}$ protein to stimulate adenylate cyclase, raising cAMP levels. Insulin, conversely, often antagonizes this process or uses tyrosine kinase pathways.

Step 4: Conclusion
Epinephrine is a classic activator of the adenylate cyclase pathway during the "fight or flight" response. Final Answer: (A)