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Question #47641
The Question
If an uncoupling agent like Dinitrophenol (DNP) is introduced to an actively photosynthesizing intact chloroplast, which of the following physiological consequences will NOT be observed?
Options
- A.
Immediate cessation of oxygen evolution due to the halting of the electron transport chain.
- B.
Accumulation of NADPH in the stroma due to the stalling of the Calvin cycle.
- C.
A decrease in the stromal pH, leading to the reduced optimal activity of RuBisCO.
- D.
Complete cessation of ATP synthesis despite continuous light absorption by the photosystems.
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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
Thylakoid Lumen|ATP Synthase|Chemiosmosis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse 'uncoupling' with 'inhibition'.
A common misconception is that if ATP synthesis stops, the entire light reaction (including the Z-scheme and water splitting) halts.
However, according to NCERT's chemiosmotic hypothesis, the ETC and proton gradient generation are upstream of ATP synthase.
Destroying the gradient stops ATP production but allows the ETC and oxygen evolution to continue, often at an accelerated rate due to the removal of proton back-pressure.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Proton Gradient Directionality |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |