The main difference between aerobic and anaerobic respiration is that aerobic respiration requires oxygen and yields 36–38 ATP per glucose molecule, while anaerobic respiration occurs without oxygen and yields only 2 ATP. NTA tests this through ATP yield calculations, end-product identification, and pathway location questions.
| Basis | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen requirement | Requires O₂ as final electron acceptor | Does not require O₂ |
| End products | CO₂ and H₂O | Ethanol + CO₂ (yeast) or lactic acid (muscles) |
| ATP yield | 36–38 ATP per glucose molecule (net) | 2 ATP per glucose molecule (net) |
| Site | Cytoplasm (glycolysis) + mitochondria (Krebs, ETC) | Cytoplasm only |
| Complete oxidation | Yes — glucose fully oxidized to CO₂ and H₂O | No — partial breakdown of glucose |
| Krebs cycle | Present | Absent |
| ETC / Oxidative phosphorylation | Present — occurs on inner mitochondrial membrane | Absent |
| Organisms | Most eukaryotes | Yeast, some bacteria, muscle cells (during oxygen debt) |
| Efficiency | High (~40% energy captured as ATP) | Low (~2% energy captured) |
| RQ (Respiratory Quotient) | 1 for carbohydrates, <1 for fats, >1 for organic acids | Infinity for anaerobic (no O₂ consumed) |
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