In anaerobic reaction of muscle, lactic acid is produced which causes painful tiredness. Where and by which mechanism lactic acid is catabolised

Options

A. In muscle by monokinase action
B. In muscle by Lohman's reaction
C. In liver by Cori cycle
D. In liver by phosphogen reaction.

Answer

**Step-by-Step Solution:**

1. **Understanding Anaerobic Respiration in Muscles:**
- During intense exercise or when oxygen levels are low, muscles rely on anaerobic respiration for energy. This process begins with the breakdown of glycogen into glucose.

2. **Glycolysis Process:**
- The glucose then enters glycolysis, a metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP (energy) in the process.

3. **Formation of Lactic Acid:**
- In the absence of oxygen, the pyruvate produced from glycolysis cannot enter the aerobic pathways (like the Krebs cycle). Instead, it is converted into lactic acid. This accumulation of lactic acid in the muscles leads to painful tiredness.

4. **Catabolism of Lactic Acid:**
- Once oxygen becomes available again, lactic acid does not remain in the muscles. It is transported to the liver, where it undergoes further processing.

5. **Conversion in the Liver:**
- In the liver, lactic acid is converted back into pyruvate. This process is part of the Cori cycle, which allows the body to recycle lactic acid back into glucose or other intermediates that can enter the Krebs cycle for further energy production.

6. **Final Pathway:**
- The pyruvate can then be converted into acetyl coenzyme A, which enters the Krebs cycle (TCA cycle) for aerobic respiration, allowing for more efficient energy production.

**Final Answer:**
Lactic acid is catabolized in the liver through the Cori cycle, where it is converted back into pyruvate.

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