Which of the following components are associated with nitrate reductase activity?
1. Reduced pyridine nucleotide
2. Flavin adenine dinucleotide
3. Molybdenum
4. Boron
Select the correct answer using the codes given below

Options

A. 1, 2 and 3
B. 1 and 2
C. 2, 3 and 4
D. 1, 3 and 4

Answer

To determine which components are associated with nitrate reductase activity, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Nitrate Reductase**:
- Nitrate reductase is an enzyme that catalyzes the conversion of nitrate (NO3-) to nitrite (NO2-). This reaction is a crucial step in the nitrogen cycle.

2. **Components Involved in Nitrate Reductase Activity**:
- The enzyme is composed of two identical subunits, each containing specific prosthetic groups that are essential for its activity.

3. **Analyzing Each Option**:
- **Option 1: Reduced Pyridine Nucleotide (NADH)**:
- This is involved in the reaction as it provides electrons for the reduction of nitrate to nitrite. Therefore, this component is associated with nitrate reductase activity.
- **Option 2: Flavin Adenine Dinucleotide (FAD)**:
- FAD is another prosthetic group present in the enzyme and plays a role in the electron transfer during the reaction. Thus, this component is also associated with nitrate reductase activity.
- **Option 3: Molybdenum**:
- Molybdenum is a critical component of nitrate reductase that enhances its activity. Hence, this component is associated with nitrate reductase activity.
- **Option 4: Boron**:
- Boron does not play any known role in the function of nitrate reductase. Therefore, this component is not associated with nitrate reductase activity.

4. **Conclusion**:
- Based on the analysis, the components that are associated with nitrate reductase activity are:
- Reduced pyridine nucleotide (NADH)
- Flavin adenine dinucleotide (FAD)
- Molybdenum
- The correct answer is options 1, 2, and 3.

### Final Answer:
The correct answer is **1, 2, and 3**.

---