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Question #46599
The Question
Which of the following statements regarding the oxygen-paradox and symbiotic nitrogen fixation in legume root nodules is INCORRECT?
Options
- A.
The enzyme nitrogenase is a Mo-Fe protein that undergoes irreversible inactivation upon exposure to molecular oxygen.
- B.
Rhizobium lives as an anaerobe under free-living conditions in the soil, but requires an aerobic environment inside the nodule to meet the high ATP demand of nitrogen fixation.
- C.
Leghemoglobin functions as an oxygen scavenger, protecting the nitrogenase enzyme by maintaining an anaerobic microenvironment.
- D.
The synthesis of ammonia requires a high energy input of 8 ATP per NH3 molecule produced, which is obtained from the respiration of host cells.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Rhizobium|Nitrogenase|Leghaemoglobin
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that because nitrogen fixation is highly energy-demanding (16 ATP per N2), the bacteria must operate aerobically inside the nodule to generate this ATP, and anaerobically in the soil.
The trap exploits this logical assumption by reversing the NCERT fact: Rhizobium is actually aerobic when free-living and anaerobic during symbiosis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | Symbiotic Nitrogen Fixation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |