What is glycolysis and where does it occur?

• A. The synthesis of glucose from pyruvate in the mitochondria.
• B. Fermentation of pyruvate to lactate in the cytoplasm.
• C. The breakdown of glucose to pyruvate, yielding ATP and NADH, in the cytoplasm.
• D. The breakdown of fatty acids to acetyl-CoA in the mitochondria.

Answer: (C)

Glycolysis is the breakdown of glucose into pyruvate in the cytoplasm, producing energy-rich molecules ATP and NADH through substrate-level phosphorylation. It happens in the cell’s cytosol and does not require oxygen, giving a net gain of 2 ATP per glucose along with 2 NADH. The pyruvate formed can then enter mitochondria for further aerobic respiration or be converted to lactate under anaerobic conditions. The other descriptions refer to different processes: making glucose from pyruvate, fermentation of pyruvate to lactate, and fatty acid breakdown in mitochondria.