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Question #47637
The Question
A researcher treats an intact plant leaf with a chemical inhibitor that specifically blocks the transfer of electrons from Ferredoxin to NADP+ reductase. Consequently, the electron transport chain defaults entirely to cyclic photophosphorylation. Which of the following represents the most accurate immediate consequence of this metabolic shift?
Options
- A.
ATP synthesis continues via chemiosmosis, but the reduction of 3-phosphoglycerate to triose phosphate in the stroma is stalled.
- B.
Oxygen evolution accelerates in the thylakoid lumen to compensate for the lack of terminal electron acceptors.
- C.
The proton gradient across the thylakoid membrane collapses, immediately halting all photophosphorylation.
- D.
The carboxylation of RuBP ceases immediately due to the absence of ATP generated by the Z-scheme.
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
Photosystem I|Photosystem II|Ferredoxin|Cyclic Photophosphorylation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often mistakenly assume that inhibiting the Z-scheme completely collapses the proton gradient and stops all light reactions.
The trap is failing to recognize that cyclic photophosphorylation 'rescues' ATP production but cannot rescue NADPH production.
This specifically bottlenecks the 'Reduction' phase of the C3 cycle, demonstrating the rigid stoichiometric requirement of NADPH for carbon fixation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Chlorophyll-a vs Accessory Pigments |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |