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Question #46949
The Question
In cyanobacteria like Nostoc, heterocysts possess a specialized thickened cell envelope that restricts oxygen entry but permits the exchange of metabolites with adjacent vegetative cells. If a hypothetical horizontal gene transfer introduced Archaebacterial cell wall properties (pseudomurein lacking N-acetylmuramic acid) into the heterocyst envelope, increasing its rigidity and altering pore-size exclusion limits, what would be the most likely physiological consequence?
Options
- A.
Nitrogenase would immediately denature due to the rapid influx of oxygen through the pseudomurein layer.
- B.
The heterocyst would successfully fix nitrogen but fail to export ammonia to adjacent vegetative cells, causing nitrogen starvation in the filament.
- C.
The heterocyst would revert to a vegetative state because pseudomurein prevents the degradation of Photosystem II.
- D.
The organism would become an obligate anaerobe as the pseudomurein wall would irreversibly bind to atmospheric oxygen.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Heterocyst|Trophic_Efficiency_Limits|Productivity_Ratios
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that Archaebacterial cell walls provide 'protection in extreme conditions' and that Heterocysts have 'thick walls' to protect nitrogenase.
The trap is assuming that making a heterocyst wall more rigid (Archaea-like) would be purely beneficial or neutral.
The pivot is realizing that heterocysts are not isolated bunkers; their survival depends entirely on selective permeability for symbiotic metabolite exchange with vegetative cells.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biological Classification - Class 11 |
| Concept | Cyanobacteria Heterocyst Function |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |