Select the correct statement regarding Cori's cycle

Options

A. Entire lactic acid is converted into glucose in muscles
B. About 1/5th of lactic acid is oxidised to CO, and water
C. Oxidative breakdown of glucose in muscles produces lactic acid
D. Both (1) & (3)

Answer

To solve the question regarding Cori's cycle, we need to analyze each of the provided options and determine which statement is correct.

### Step-by-Step Solution:

1. **Understanding Cori's Cycle**:
- The Cori's cycle is a metabolic pathway that describes the conversion of lactate produced in muscles during anaerobic glycolysis into glucose in the liver. This glucose can then be transported back to the muscles for energy.

2. **Analyzing Each Option**:
- **Option 1**: "Entire lactic acid is converted into glucose in muscles."
- This statement is incorrect. Not all lactic acid is converted into glucose in muscles; some of it is transported to the liver for conversion.

- **Option 2**: "About one-fifth of lactic acid is oxidized to CO2 and water."
- This statement is correct. A portion of lactic acid can be oxidized in the liver to produce carbon dioxide and water.

- **Option 3**: "Oxidative breakdown of glucose in muscles produces lactic acid."
- This statement is partially correct but misleading. While glucose can be broken down anaerobically to produce lactic acid, the term "oxidative breakdown" typically refers to aerobic respiration, which does not produce lactic acid.

- **Option 4**: "Both 1 and 3."
- Since Option 1 is incorrect, Option 4 cannot be correct either.

3. **Conclusion**:
- The correct answer is Option 2: "About one-fifth of lactic acid is oxidized to CO2 and water."

### Final Answer:
The correct statement regarding Cori's cycle is Option 2: "About one-fifth of lactic acid is oxidized to CO2 and water."