5. a) Explain why is it not possible for human muscles to continue working for extended periods of time without oxygen. (2 points) Because without oxygen the muscles have to rely on acid lactic fermentation. Even though acid lactic fermentation does not provide near as much ATP as the aerobic energy cycle would. Since the acid lactic fermentation cycle creates much less energy than the aerobic energy cycle does, this is why it is not possible for the muscles to continue working for too long relying on the acid lactic fermentation.

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