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AQA A-Level PE Energy Systems Practice Exam

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How many molecules of ATP are produced as a net yield per glucose during the short-term lactate anaerobic system (anaerobic glycolysis)?
Correct Answer:
2
Explanation:
The key idea is that anaerobic glycolysis provides energy only through substrate-level phosphorylation in glycolysis itself, because there is no oxygen for oxidative phosphorylation. Glucose is broken down to lactate in the cytoplasm, and this pathway yields a net 2 ATP per glucose: four ATP are produced during glycolysis, but two are used in the early steps, so the net gain is two. The NADH produced is used to convert pyruvate to lactate, regenerating NAD+ to keep glycolysis going, but it does not generate additional ATP in the absence of oxygen. In contrast, the 36 ATP figure comes from full aerobic respiration, which isn’t happening here. So the net ATP yield per glucose in the short-term lactate anaerobic system is two.

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