Question 4

The burning sensation associated with anaerobic respiration is caused by lactic acid.

During anaerobic respiration, glucose is broken down without the presence of oxygen, leading to the production of lactic acid. This accumulation of lactic acid in the muscles is what creates the burning sensation often experienced during intense exercise.

A) Carbon dioxide

Carbon dioxide is a byproduct of both aerobic and anaerobic respiration but does not directly cause the burning sensation. While it can contribute to feelings of fatigue, it is not the primary cause of the discomfort associated with anaerobic respiration.

B) Lactic acid

Lactic acid is the correct answer as it is produced when glucose is metabolized anaerobically. The build-up of lactic acid in the muscles lowers the pH, leading to the characteristic burning sensation during strenuous activities.

C) Oxygen

Oxygen is not present during anaerobic respiration, and its absence is what necessitates anaerobic processes. It does not contribute to the burning sensation; in fact, the presence of oxygen typically helps to prevent the build-up of lactic acid and related discomfort.

D) Glucose

Glucose is the substrate used in both aerobic and anaerobic respiration but is not responsible for the burning sensation. Instead, it is the breakdown of glucose and subsequent production of lactic acid that leads to the sensation of burning in the muscles.

Conclusion

Lactic acid is definitively the cause of the burning sensation during anaerobic respiration, as it directly results from glucose metabolism in the absence of oxygen. Other options, such as carbon dioxide, oxygen, and glucose, do not produce this effect and therefore do not accurately explain the physiological response in question.