Question

What is the function of leghemoglobin present in root nodulus of leguminous plants?

• A. Inhibition of nitrogenase activity
• B. Removal of oxygen
• C. Nodule differentiation.
• D. Expression of nif gene

Hint:

Think of leghemoglobin as the nodule's "security guard" for the nitrogenase enzyme. Its job is to keep the enemy (free oxygen) away from the enzyme so it can do its work, while still letting the bacteria breathe.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question asks for the specific role of leghemoglobin, a protein found in the root nodules of nitrogen-fixing leguminous plants.
Step 2: Detailed Explanation:
Symbiotic nitrogen fixation presents a paradox: the nitrogen-fixing bacteria (Rhizobium) are aerobic and require oxygen for cellular respiration to produce the large amounts of ATP needed for nitrogen fixation. However, the key enzyme for this process, nitrogenase, is extremely sensitive to oxygen and is irreversibly inactivated by it.
Leghemoglobin solves this problem. It is an oxygen-binding protein, similar to hemoglobin in animal blood, that gives the active nodules their characteristic pink/red color. Its function is to act as an "oxygen buffer" or "oxygen scavenger". It binds strongly to free oxygen in the nodule, maintaining a very low concentration of free O\(_2\). This protects the nitrogenase enzyme from damage while still delivering a steady supply of oxygen to the bacterial electron transport chain for respiration.
Therefore, its function is the effective removal or sequestration of free oxygen from the immediate environment of the nitrogenase enzyme.
Step 3: Final Answer:
The function of leghemoglobin is the removal of free oxygen to protect the nitrogenase enzyme.