During intense muscle exercise, glucose is catabolized anaerobically. The regeneration of NAD+ in the cytoplasm is essential for glycolysis to continue. Which reaction specifically regenerates cytoplasmic NAD+ under anaerobic conditions in skeletal muscle?

• A Pyruvate is reduced to lactate by lactate dehydrogenase ✓
• B Pyruvate is converted to oxaloacetate by pyruvate carboxylase
• C Pyruvate is converted to acetyl-CoA by pyruvate dehydrogenase
• D Glucose-6-phosphate is oxidized by glucose-6-phosphate dehydrogenase

Explanation

Under anaerobic conditions, oxidative phosphorylation is insufficient to reoxidize NADH. Lactate dehydrogenase reduces pyruvate to lactate, simultaneously oxidizing NADH to NAD+. This cytoplasmic regeneration of NAD+ is indispensable for glycolysis to proceed, since glyceraldehyde-3-phosphate dehydrogenase requires NAD+ as a cofactor.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.