Ch 12 covers cellular respiration in plants — glycolysis, the TCA (Krebs) cycle, the electron transport chain, oxidative phosphorylation, and anaerobic respiration (fermentation).
Glycolysis (Embden-Meyerhof pathway, cytoplasm): glucose → 2 pyruvate + 2 ATP + 2 NADH (net). No O₂ needed. Pyruvate → acetyl CoA (by pyruvate dehydrogenase, produces NADH + CO₂). Krebs cycle (TCA cycle, mitochondrial matrix): acetyl CoA → 2CO₂ + 3NADH + 1FADH₂ + 1GTP per turn. Two turns per glucose.
Electron Transport Chain (inner mitochondrial membrane): NADH donates electrons → Complexes I-IV → O₂ is final electron acceptor → H₂O formed. Proton gradient drives ATP synthase (chemiosmosis). Total yield: ~36-38 ATP per glucose. Fermentation (anaerobic): pyruvate → ethanol + CO₂ (yeast) or lactic acid (animal muscles). Only 2 ATP (from glycolysis).
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Oxygen is the final electron acceptor in the electron transport chain. Without O₂, electrons cannot flow through the chain, NADH and FADH₂ cannot be recycled, and the Krebs cycle stops. ATP production drops from ~36-38 (aerobic) to just 2 (anaerobic fermentation). O₂ accepts electrons and combines with H⁺ to form water.
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