Which process uses glucose to produce pyruvate and a small amount of ATP without oxygen?

• A. Glycolysis
• B. Fermentation
• C. Electron Transport Chain
• D. Krebs Cycle

Answer: (A)

Glycolysis is the process that uses glucose to produce pyruvate and a small amount of ATP without oxygen. It happens in the cytosol and does not require oxygen, breaking one glucose molecule into two pyruvate molecules. The net energy yield is 2 ATP per glucose produced by substrate-level phosphorylation, along with 2 NADH. In anaerobic conditions, glycolysis can continue only if NADH is reoxidized to NAD+, which in many cells happens via fermentation—converting pyruvate into lactate or other end products—which regenerates NAD+ but doesn’t produce more pyruvate itself. The other options don’t fit: the Krebs cycle and electron transport chain rely on oxygen, and fermentation uses pyruvate produced by glycolysis rather than generating pyruvate from glucose.