Biological oxidation in Kreb's cycle involves

Options

A. `N_(2)`
B. `O_(2)`
C. `SO_(2)`
D. `CO_(2)`.

Answer

To answer the question "Biological oxidation in Kreb's cycle involves," we need to analyze the options provided: nitrogen, oxygen, sulfur dioxide, and carbon dioxide.

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

2. **Role of Oxygen**: The Krebs cycle requires oxygen to function. It is an aerobic process, meaning it occurs in the presence of oxygen. Without oxygen, the cycle cannot proceed, and the organism will resort to anaerobic processes like fermentation.

3. **Analyzing Each Option**:
- **Nitrogen**: Nitrogen does not play a direct role in the Krebs cycle. It is not involved in the oxidation process.
- **Oxygen**: Oxygen is essential for the Krebs cycle as it is involved in the biological oxidation of substrates. Thus, this is a correct option.
- **Sulfur Dioxide**: Sulfur dioxide is not involved in the Krebs cycle and does not contribute to biological oxidation.
- **Carbon Dioxide**: Carbon dioxide is produced as a byproduct of the Krebs cycle but is not involved in the oxidation process itself. It is an end product, not a reactant.

4. **Conclusion**: The only element that is directly involved in the biological oxidation during the Krebs cycle is oxygen. Therefore, the correct answer is **oxygen**.

### Final Answer:
Biological oxidation in the Krebs cycle involves **oxygen**.