AMP-activated protein kinase (AMPK) acts as an energy sensor. When activated by a high AMP:ATP ratio, which combination of metabolic effects does it produce?

• A Activates acetyl-CoA carboxylase (ACC) and HMG-CoA reductase; inhibits fatty acid oxidation
• B Inhibits ACC (reducing malonyl-CoA, relieving CPT-1 inhibition) and inhibits HMG-CoA reductase; promotes fatty acid oxidation and glucose uptake ✓
• C Activates glycogen synthase and inhibits glycogen phosphorylase, promoting glycogen storage
• D Inhibits hexokinase and activates gluconeogenesis via PEPCK upregulation

Explanation

AMPK, activated by energy depletion (high AMP:ATP), phosphorylates and inactivates acetyl-CoA carboxylase (ACC), reducing malonyl-CoA production. Since malonyl-CoA inhibits carnitine palmitoyltransferase-1 (CPT-1), AMPK activation relieves this inhibition and promotes mitochondrial fatty acid import and beta-oxidation. AMPK also phosphorylates and inhibits HMG-CoA reductase (limiting cholesterol synthesis) and promotes GLUT4 translocation to increase glucose uptake. Metformin and exercise both activate AMPK. Conversely, when ATP is abundant, AMPK is inactive, allowing anabolic pathways.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.