Cellular Respiration & ATP Synthesis

How cells harvest energy from glucose

Cellular respiration harvests energy from glucose in three stages. Glycolysis (cytoplasm): glucose (6C) is split into two pyruvate (3C), producing 2 ATP and 2 NADH. The Pyruvate Oxidation step converts pyruvate to Acetyl-CoA, releasing CO₂. The Krebs Cycle (mitochondrial matrix): each Acetyl-CoA enters, and per cycle produces 3 NADH, 1 FADH₂, 1 ATP, and 2 CO₂. The Electron Transport Chain (inner mitochondrial membrane): NADH and FADH₂ donate electrons through protein complexes, pumping H⁺ into the intermembrane space. The proton gradient drives ATP synthase, producing ~26-28 ATP. Total yield: ~30-32 ATP per glucose (aerobic). Without O₂, fermentation produces only 2 ATP.