Which of the following correctly pairs the signaling molecule with its function?

• A. AMPK - it inhibits glucose uptake
• B. AMPK - it stimulates glucose uptake and fatty acid oxidation
• C. AMPK - it reduces mitochondrial biogenesis
• D. AMPK - it prevents antioxidant enzyme synthesis

Answer: (B)

AMPK functions as an energy sensor that activates pathways to restore cellular energy when ATP is low. When AMPK is activated, it increases glucose uptake by promoting GLUT4 translocation to the cell membrane, and it boosts fatty acid oxidation by inhibiting acetyl-CoA carboxylase, lowering malonyl-CoA levels and freeing CPT1 to import fatty acids into mitochondria for oxidation. These coordinated actions help muscle use both glucose and fats efficiently during energy stress, such as exercise. AMPK can also promote mitochondrial biogenesis through pathways like PGC-1alpha, enhancing oxidative capacity. The other options don’t fit because AMPK does not inhibit glucose uptake, and it is associated with increased, not reduced, mitochondrial biogenesis and antioxidant responses.