Which of the following defines the term glycolysis?

• A. Conversion of glucose into lactate or pyruvate
• B. Conversion of glucose to glycogen
• C. Breakdown of glycogen to form glucose
• D. Breakdown of lipids to form glucose

Answer: (A)

Glycolysis is the process that breaks down a glucose molecule into smaller molecules—specifically pyruvate or lactate—while producing a small amount of ATP and NADH in the cytoplasm. This is why the description of converting glucose into lactate or pyruvate best captures what glycolysis does. In aerobic conditions, pyruvate can then enter the mitochondria for further oxidation; in anaerobic conditions, pyruvate is reduced to lactate to keep glycolysis going by regenerating NAD+. The other options describe different metabolic routes: converting glucose to glycogen is glycogenesis, breaking down glycogen to glucose is glycogenolysis, and breaking down lipids to form glucose involves lipid metabolism and gluconeogenesis rather than glycolysis.