Cellular Respiration — Making ATP

Complete glucose oxidation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~30–32 ATP

Stage 1: Glycolysis (cytoplasm)

Glucose (6C) → 2 pyruvate (3C)

Net: 2 ATP, 2 NADH

Does NOT require oxygen

Stage 2: Pyruvate decarboxylation (mitochondrial matrix)

2 Pyruvate → 2 Acetyl-CoA + 2 CO₂

Produces 2 NADH

Stage 3: Krebs Cycle / Citric Acid Cycle (matrix)

Per glucose: 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂

Stage 4: Electron Transport Chain (inner mitochondrial membrane)

NADH and FADH₂ donate electrons

Electrons flow through Complex I → II → III → IV

Proton gradient drives ATP synthase (chemiosmosis)

Final electron acceptor: O₂ → H₂O

~26–28 ATP produced here

Anaerobic: Fermentation

No oxygen → pyruvate → lactate (animals) or ethanol + CO₂ (yeast)

Regenerates NAD⁺ to keep glycolysis running

Reference:

Wikipedia: Cellular Respiration

https://en.wikipedia.org/wiki/Cellular_respiration