Glucagon binds its GPCR on hepatocytes. The immediate downstream consequence that activates protein kinase A (PKA) is production of which second messenger?

• A Diacylglycerol (DAG)
• B Cyclic AMP (cAMP) ✓
• C Inositol-1,4,5-trisphosphate (IP3)
• D Cyclic GMP (cGMP)

Explanation

Glucagon binds a Gs-coupled GPCR; the Gsα subunit activates adenylyl cyclase, converting ATP to cyclic AMP. cAMP activates PKA, which phosphorylates (inactivates) glycogen synthase and (activates) glycogen phosphorylase kinase, net promoting glycogenolysis and gluconeogenesis. DAG and IP3 are products of PLC activation via Gq, used by vasopressin (V1), angiotensin II, and others. cGMP mediates nitric oxide and ANP signalling.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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