The Question is from neet-botany mineral-nutrition n2-metab0lism, and it was created by the author NISHANTH

Question

Leghaemoglobin is present in the root nodules of leguminous plants. What is its primary function?

NISHANTH · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Nitrogen fixation in leguminous plants
 **Related Topics**: Root nodules, leghemoglobin, nitrogenase, oxygen sensitivity
 **Prerequisites**: Basic understanding of plant physiology and the nitrogen cycle.
## SOLUTION PATHWAY
**Given Information**:
  Leghaemoglobin is present in the root nodules of leguminous plants.
  Options describe different functions related to nitrogen fixation.
**Method & Steps**:
 1. Understand the role of nitrogen fixation in leguminous plants.
  Reasoning: Leguminous plants have a symbiotic relationship with nitrogen-fixing bacteria (Rhizobia) residing in their root nodules. These bacteria convert atmospheric nitrogen ($N_2$) into ammonia ($NH_3$), a usable form of nitrogen for plants. This process is called nitrogen fixation.
 2. Identify the function of leghaemoglobin.
  Working: Leghaemoglobin is an oxygen-binding protein. Its structure is similar to haemoglobin in animals.  It is crucial for nitrogen fixation because the enzyme responsible, nitrogenase, is extremely sensitive to oxygen.  Oxygen inhibits nitrogenase activity.
  Key Point: Leghaemoglobin maintains a low oxygen concentration within the root nodules, creating a microaerophilic environment that protects nitrogenase.
 3. Determine the primary function of leghaemoglobin.
  Result: The primary function of leghaemoglobin is to protect nitrogenase from oxygen.
  Verification: This aligns with the established understanding of the symbiotic relationship between leguminous plants and nitrogen-fixing bacteria and the oxygen sensitivity of nitrogenase.
 ## OPTION ANALYSIS
A :x:  While leghaemoglobin is present in nodules where nitrogen fixation occurs, its function isn't directly to *fix* nitrogen. Nitrogen fixation is performed by the nitrogenase enzyme.
B ✓:  This is the correct answer.  Leghaemoglobin's main role is to regulate oxygen levels, protecting the oxygen-sensitive nitrogenase.
C :x: Nitrate reduction to nitrite is a different step in the nitrogen cycle, occurring after nitrogen fixation.
D :x: Leghaemoglobin doesn't directly provide energy for nitrogen fixation. Energy is supplied through respiration and photosynthesis.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the role of leghaemoglobin with the role of nitrogenase:  Students might think leghaemoglobin directly fixes nitrogen.
  How to avoid: Remember that leghaemoglobin is an oxygen-binding protein, not an enzyme that catalyzes nitrogen fixation.
  2.Overlooking the oxygen sensitivity of nitrogenase:  Students might not understand why a low-oxygen environment is crucial for nitrogen fixation.
  How to avoid: Focus on the sensitivity of nitrogenase to oxygen and how leghaemoglobin helps create the right conditions.
 **Quick Tips**:
  1.Think of leghaemoglobin as a 'protective shield' for nitrogenase.
  2.Remember the analogy to haemoglobin – both bind oxygen, but serve different purposes.

NISHANTH · Answer

Fix atmospheric nitrogen

NISHANTH · Answer

The correct Option is "Protect nitrogenase from oxygen"

NISHANTH · Answer

Convert nitrate to nitrite

NISHANTH · Answer

Provide energy for nitrogen fixation

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