Lactic acid is produced by anaerobic metabolism of which substrate?

Lactic acid is produced by anaerobic metabolism of which substrate?

• A. Aerobic metabolism of glucose
• B. Fatty acid oxidation
• C. Protein catabolism
• D. Anaerobic metabolism of glucose

Answer: (D)

When oxygen is limited, muscles switch to anaerobic glycolysis. Glucose is broken down to pyruvate, and in the absence of enough oxygen pyruvate is converted to lactate (lactic acid) to regenerate NAD+, allowing glycolysis to continue and a small amount of ATP to be produced. This means lactic acid comes from glucose under anaerobic conditions. Aerobic metabolism of glucose would fully oxidize it to CO2 and water and wouldn’t produce lactate; other pathways like fatty acid oxidation or protein breakdown follow different routes and don’t generate lactate in this immediate anaerobic context.

When oxygen is limited, muscles switch to anaerobic glycolysis. Glucose is broken down to pyruvate, and in the absence of enough oxygen pyruvate is converted to lactate (lactic acid) to regenerate NAD+, allowing glycolysis to continue and a small amount of ATP to be produced. This means lactic acid comes from glucose under anaerobic conditions. Aerobic metabolism of glucose would fully oxidize it to CO2 and water and wouldn’t produce lactate; other pathways like fatty acid oxidation or protein breakdown follow different routes and don’t generate lactate in this immediate anaerobic context.