Cornell Note — Respiration in Plants Overview — Notes

Citric Acid (Krebs) Cycle — central stage of aerobic cellular respiration Image: Cellular respiration overview — Wikimedia Commons (public domain)

Cue Column | Notes Column

Cue / Question	Notes
What is cellular respiration?	Controlled oxidation of organic molecules to release energy in a stepwise manner; $C_{6}H_{12}O_{6}$ + $6O_{2}$ → $6CO_{2}$ + $6H_{2}O$ + Energy (ATP)
How many stages?	4 stages: Glycolysis → Oxidative decarboxylation → TCA cycle → ETS + Oxidative phosphorylation
What is different from combustion?	Combustion is uncontrolled, releases energy as heat in one step; cellular respiration is stepwise, trapping energy as ATP (~40% efficiency)
Where does each stage occur?	Glycolysis: cytoplasm; Link reaction + TCA: mitochondrial matrix; ETS: inner mitochondrial membrane
Total ATP from one glucose?	38 ATP (theoretical maximum); 36 ATP if glycerol-3-phosphate shuttle used
Why is $O_{2}$ needed?	As the final electron acceptor in ETS (at Complex IV); without $O_{2}$ , ETS stops and only 2 ATP from fermentation

Summary (Bottom Section)

Cellular respiration converts the chemical energy of glucose into ATP through four integrated stages. Glycolysis (cytoplasm) is common to all organisms; the remaining stages require mitochondria and $O_{2}$ . The electron carriers NADH and $FADH_{2}$ ferry electrons to the ETS, where chemiosmosis (Peter Mitchell) drives ATP synthesis via $F_{0}$ - $F_{1}$ ATP synthase. Total yield: 38 ATP per glucose.