Read the extract below and answer the questions that follow:

Aerobic and anaerobic respiration are used to supply energy during exercise. During certain types of exercise, for example, athletics events such as 100m, 200m, 1500m, and 3000m, the muscles are unable to obtain sufficient oxygen for the removal of large quantities of lactic acid from their cells. When sprinting, an athlete cannot possibly inhale more than a fraction of the oxygen required, and the body goes into 'oxygen debt'. This debt can only be repaid by rapid breathing after the sprint ends.

3.2.1 Which athletic event relies the most on anaerobic respiration? (1)

3.2.2 Explain your answer in QUESTION 3.2.1 above. (2)

3.2.3 Name TWO end products of aerobic respiration in muscle cells. (2)

3.2.4 Explain what you understand by the term 'oxygen debt'. (2)

3.2.5 Tabulate TWO differences between aerobic and anaerobic respiration.

3.2.2 The 100m sprint is a short and intense burst of activity. During such high-intensity exercise, the body cannot supply enough oxygen to the muscles quickly enough to meet their energy needs through aerobic respiration alone. As a result, the muscles depend heavily on anaerobic respiration, which does not require oxygen and allows for rapid generation of ATP (energy). However, this process leads to the accumulation of lactic acid. (2)

3.2.3 Two end products of aerobic respiration in muscle cells are carbon dioxide (CO₂) and water (H₂O). (2)

3.2.4 'Oxygen debt' refers to the amount of extra oxygen that the body needs after exercise to restore it to its normal, resting state. This involves converting the accumulated lactic acid back into pyruvate, replenishing the creatine phosphate levels in muscles, and resaturating myoglobin with oxygen, among other processes. This is why athletes breathe rapidly post-exercise; they're trying to repay their 'oxygen debt.' (2)

3.2.5 Differences between aerobic and anaerobic respiration:

**Oxygen Requirement: **
- Aerobic Respiration: Requires oxygen.
- Anaerobic Respiration: Does not require oxygen.
End Products:
- Aerobic Respiration: Produces carbon dioxide and water.
- Anaerobic Respiration: Produces lactic acid in muscles.
Energy Yield:
- Aerobic Respiration: Produces more energy (about 36-38 ATP molecules per glucose molecule).
- Anaerobic Respiration: Produces less energy (about 2 ATP molecules per glucose molecule).