AMP-activated protein kinase (AMPK) is called the cellular energy sensor. In conditions of energy depletion, AMPK activation switches on catabolic pathways. Which combination best describes AMPK's actions?

• A Activates fatty acid synthesis; inhibits fatty acid oxidation; activates mTORC1
• B Inhibits fatty acid synthesis (ACC phosphorylation); activates fatty acid oxidation; inhibits mTORC1; activates autophagy ✓
• C Activates glycogen synthesis; inhibits gluconeogenesis; activates ribosomal biogenesis
• D Inhibits GLUT4 translocation; activates cholesterol synthesis; inhibits autophagy

Explanation

AMPK is activated when AMP:ATP ratio rises (energy deficit). It phosphorylates and inactivates acetyl-CoA carboxylase (ACC), reducing malonyl-CoA synthesis. Malonyl-CoA is an allosteric inhibitor of CPT-1 (carnitine palmitoyl transferase-1); when malonyl-CoA falls, CPT-1 activity increases, allowing fatty acids to enter mitochondria for beta-oxidation. AMPK simultaneously inhibits mTORC1 (blocking anabolic protein synthesis and ribosome biogenesis), inhibits cholesterol synthesis (via HMG-CoA reductase phosphorylation), activates ULK1 to initiate autophagy, and enhances GLUT4 translocation to increase glucose uptake. All these effects restore energy balance by increasing catabolism and suppressing anabolism.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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