Select the incorrect statement with respect to the biological nitrogen fixation by Rhizobium

Options

A. Nitrogenase may require oxygen for its functioning
B. Nitrogenase is Mo - Fe protein
C. Leg - haemoglobin is a pink - coloured pigment
D. Nitrogenase helps to convert ` N_ 2 ` gas into two molecules of ammonia

Answer

To solve the question, we need to identify the incorrect statement regarding biological nitrogen fixation by Rhizobium. Let's break down the information provided in the video transcript step by step.

### Step 1: Understand Biological Nitrogen Fixation
Biological nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by certain bacteria, including Rhizobium. This process is crucial for enriching soil with nitrogen, which is an essential nutrient for plants.

**Hint:** Remember that nitrogen fixation is the conversion of atmospheric nitrogen into a usable form for plants.

### Step 2: Identify the Role of Rhizobium
Rhizobium is a type of bacteria that forms a symbiotic relationship with the roots of leguminous plants. In this relationship, Rhizobium helps the plant by fixing nitrogen, while the plant provides the bacteria with carbohydrates and a suitable environment to thrive.

**Hint:** Consider the mutual benefits of the symbiotic relationship between Rhizobium and leguminous plants.

### Step 3: Recognize the Importance of Nitrogenase
The enzyme nitrogenase is essential for the nitrogen fixation process. It catalyzes the conversion of nitrogen gas into ammonia. This enzyme operates in anaerobic conditions, meaning it does not function well in the presence of oxygen.

**Hint:** Focus on the role of nitrogenase and its requirement for anaerobic conditions.

### Step 4: Understand the Role of Leghemoglobin
Leghemoglobin is a pink pigment found in the root nodules of leguminous plants where Rhizobium resides. It acts as an oxygen scavenger, binding oxygen and creating an anaerobic environment necessary for nitrogenase to function.

**Hint:** Remember that leghemoglobin helps maintain the low oxygen levels needed for nitrogen fixation.

### Step 5: Evaluate the Statements
Now, let's evaluate the statements provided in the question:
1. Leghemoglobin is a pink color pigment.
2. Nitrogen is converted into two molecules of ammonia.
3. Nitrogenase is a molybdenum-iron protein.
4. Nitrogenase requires oxygen.

From the evaluation:
- The first three statements are true.
- The fourth statement is incorrect because nitrogenase does not require oxygen; it actually requires an anaerobic environment to function.

### Conclusion
The incorrect statement with respect to biological nitrogen fixation by Rhizobium is that "Nitrogenase requires oxygen."

**Final Answer:** Nitrogenase requires oxygen (this statement is incorrect).

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