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Question #47592
The Question
An agricultural scientist applies an herbicide that competitively binds to the plastoquinone-binding site on Photosystem II of a C3 weed. Which of the following statements INCORRECTLY describes the subsequent physiological consequences in the treated plant?
Options
- A.
The splitting of water on the inner side of the thylakoid membrane halts due to an electron backup, stopping the release of protons into the lumen.
- B.
Plastoquinone fails to act as a hydrogen carrier, preventing the cytochrome b6f complex from translocating protons from the stroma to the lumen.
- C.
The proton gradient across the thylakoid membrane reaches a maximum, but ATP synthesis halts due to the direct allosteric inhibition of the CF0 transmembrane channel.
- D.
Due to the cessation of the Calvin cycle from ATP and NADPH starvation, the plant prematurely reaches its compensation point and acts as a net carbon source.
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
Photolysis of Water Stoichiometry|Competitive Enzyme Inhibition Kinetics|Compensation Point Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Misconception Trap: Students often confuse the cause of ATP synthase failure.
A common misconception is that if ATP is not being synthesized, the enzyme itself must be blocked, leading to a backlog (accumulation) of protons.
In reality, blocking the ETC upstream at PSII prevents the proton gradient from forming in the first place, leading to a collapse of the proton motive force, not an accumulation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Photolysis of Water Stoichiometry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |