Bill goes on an 8-hour continuous, moderate-intensity hike. Most of the ATP for this activity will be derived from

Question

BlackTom AI · Accepted Answer

Question restated: Bill goes on an 8-hour continuous, moderate-intensity hike. Most of the ATP for this activity will be derived from which energy source?

Option 1: breakdown of amino acids. This is unlikely for sustained endurance activity because amino acid oxidation contributes only a small portion of energy during steady-state aerobic exercise; amino acids are generally spared for protein synthesis and only used for energy under extreme or prolonged starvation, not as the primary fuel during a hike.

Option 2: breakdown of fatty acids. Correct reasoning: during long-duration, moderate-intensity exercise, the body relies heavily on fat oxidation to meet ATP demands because fat stores provide a large, relatively abundant energy source and can be mobilized efficiently with adequate oxygen. As exercise continues, fat becomes the dominant substrate, provided intensity remains at moderate levels.

Option 3: anaerobic glucose breakdown. This pathway is characteristic of high-intensity, short-duration efforts when oxygen delivery is insufficient for complete glucose oxidation. An 8-hour hike at moderate intensity is not anaerobic; oxygen supply is adequate, so anaerobic pathways contribute little energy.

Option 4: aerobic glucose breakdown. While aerobic glycolysis does occur during endurance exercise, it typically provides a smaller fraction of energy compared to fat oxidation at moderate intensities over long durations. Glucose oxidation is faster but less abundant in fuel energy density than fat over many hours, so fat predominates.

In summary, for an extended, moderate-effort activity like an 8-hour hike, the body shifts toward greater fat oxidation, making breakdown of fatty acids the primary ATP source. Each of the other options either describes a minor or inappropriate energy pathway for this scenario, given the duration and intensity.

Bill goes on an 8-hour continuous, moderate-intensity hike. Most of the ATP for this activity will be derived from单项选择题

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