A level Biology B · Edexcel 9BI0 · Topic 5B
Aerobic and anaerobic respiration
Key points
- Glycolysis (cytoplasm): glucose is phosphorylated and split into two pyruvate, giving a net gain of 2 ATP and 2 reduced NAD.
- Link reaction (mitochondrial matrix): pyruvate is decarboxylated and dehydrogenated to acetyl CoA.
- Krebs cycle (matrix): acetyl CoA joins oxaloacetate; the cycle releases CO and makes reduced NAD, reduced FAD and ATP.
- Oxidative phosphorylation (inner membrane/cristae): electrons pass along the electron transport chain, protons are pumped into the intermembrane space and flow back through ATP synthase (chemiosmosis). Oxygen is the final electron acceptor, forming water.
- Without oxygen, pyruvate is reduced to lactate (animals) or ethanol and CO (yeast) to regenerate NAD; lactate is later converted back in the liver.
- RQ: about 1.0 for carbohydrate, 0.7 for lipid; measure oxygen uptake with a respirometer.
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Respiration releases energy from organic molecules to make ATP. Aerobic respiration oxidises glucose completely to carbon dioxide and water in four linked stages; anaerobic respiration only completes the first stage, so it yields far less…
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