In Which step, `CO_2` is not released ?

Options

A. (a) Glycolysis
B. (b) Lactic acid fermentation
C. (c) Oxidation of malic acid into OAA
D. (d) All of the above

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks in which step carbon dioxide (CO2) is not released during the process of respiration in plants.

2. **Analyzing Option A - Glycolysis**:
- Glycolysis is the process where glucose is converted into pyruvate.
- During this process, ATP and NADH are produced.
- Importantly, no carbon dioxide is released in glycolysis.
- **Conclusion**: CO2 is not released in glycolysis.

3. **Analyzing Option B - Lactic Acid Fermentation**:
- This process begins with glycolysis, where glucose is converted to pyruvate.
- The pyruvate is then converted to lactate (lactic acid).
- Similar to glycolysis, this process also does not release carbon dioxide.
- **Conclusion**: CO2 is not released in lactic acid fermentation.

4. **Analyzing Option C - Oxidation of Malic Acid to Oxaloacetate**:
- This reaction occurs in the Krebs cycle, where malic acid is oxidized to form oxaloacetate.
- During this reaction, NADH is produced, but no carbon dioxide is released.
- **Conclusion**: CO2 is not released in the oxidation of malic acid to oxaloacetate.

5. **Final Conclusion**:
- Since all three options (A, B, and C) do not involve the release of carbon dioxide, we can conclude that the answer to the question is that CO2 is not released in any of these steps.
- Therefore, the correct answer is **D** (none of the above).