During strenuous anaerobic exercise, the pyruvate produced by glycolysis is preferentially converted to lactate in skeletal muscle. The primary biochemical purpose of this conversion is to:

• A Regenerate NAD+ to sustain continued glycolysis ✓
• B Generate additional ATP beyond substrate-level phosphorylation
• C Feed pyruvate into the TCA cycle
• D Produce alanine for hepatic gluconeogenesis

Explanation

Under anaerobic conditions, the mitochondrial electron transport chain cannot reoxidize NADH at sufficient rates. Lactate dehydrogenase converts pyruvate to lactate while simultaneously oxidizing NADH back to NAD+. This regeneration of NAD+ is essential to maintain the cytosolic redox balance needed for continued flux through glycolysis, the only ATP-generating pathway available without oxygen.

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

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