OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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Where does anaerobic respiration primarily take place in humans?

  1. During resting periods

  2. In short, intense exercises

  3. While sleeping

  4. During long distance exercise

The correct answer is: During long distance exercise

Anaerobic respiration primarily occurs in humans during short, intense exercises when the body requires energy at a rate that exceeds the capacity of oxygen to supply it. In these situations, the body shifts to anaerobic respiration to quickly produce ATP (adenosine triphosphate), the energy currency of the cell, without relying on oxygen. This process allows for sustained energy output during high-intensity activities, such as sprinting or lifting heavy weights, where the demand for energy is immediate and significant. During long-distance exercise, the body typically relies on aerobic respiration, which uses oxygen more efficiently to generate energy. In contrast, resting periods and sleeping involve a lower level of metabolic activity, favoring aerobioc respiration processes as well. Therefore, anaerobic conditions do not align with these more leisurely states of activity.