In the context of cellular respiration, how is oxygen debt paid back after intense exercise?

• A. By increasing the rate of glycolysis in muscle cells
• B. By storing excess oxygen in muscle tissues
• C. By converting lactic acid back into pyruvate in the liver
• D. By producing more ATP through anaerobic pathways

Answer: (C)

Verified step by step guidance

1. Understand that during intense exercise, the body may not supply enough oxygen to the muscles, leading to anaerobic respiration and the production of lactic acid.
2. Recognize that 'oxygen debt' refers to the amount of extra oxygen the body needs after exercise to restore metabolic conditions to pre-exercise levels.
3. Identify that one way the body repays this oxygen debt is by converting lactic acid back into pyruvate, which can then enter the aerobic respiration pathway.
4. Note that this conversion primarily occurs in the liver, where lactic acid is transported from the muscles and converted back into pyruvate.
5. Acknowledge that this process requires oxygen, which is why increased oxygen intake after exercise helps in 'paying back' the oxygen debt.