Name the element that plays an important role in biological nitrogen fixation

Options

A. molybdenum
B. manganese
C. copper
D. zinc

Answer

**Step-by-Step Solution:**

1. **Understand the Concept of Biological Nitrogen Fixation:**
- Biological nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds in soil and water, primarily by certain bacteria and archaea.

2. **Identify the Elements Involved in Nitrogen Fixation:**
- Various elements play roles in the process of nitrogen fixation, including molybdenum, manganese, copper, and zinc.

3. **Evaluate Each Element:**
- **Molybdenum (Mo):**
- Molybdenum is crucial for nitrogen metabolism and is known to activate the enzyme nitrate reductase, which is essential for the conversion of nitrate to ammonia. This makes it a key player in biological nitrogen fixation.
- **Manganese (Mn):**
- Manganese is important for plant growth, but it does not directly participate in the nitrogen fixation process.
- **Copper (Cu):**
- Copper is necessary for various plant functions, but its deficiency leads to chlorosis (yellowing of leaves) and does not play a direct role in nitrogen fixation.
- **Zinc (Zn):**
- Zinc is involved in plant growth and development but does not directly contribute to the nitrogen fixation process.

4. **Conclusion:**
- Based on the evaluation, molybdenum is the element that plays an important role in biological nitrogen fixation. Therefore, the correct answer is **molybdenum**.

**Final Answer: Molybdenum**

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