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Question #47616
The Question
A C3 plant actively undergoing photorespiration is treated with an inhibitor that specifically blocks Cytochrome c oxidase (Complex IV) in the electron transport chain. Which of the following best describes the immediate synergistic consequence on the plant's carbon metabolism?
Options
- A.
Collapse of the mitochondrial proton motive force halts NADH oxidation and ATP synthesis, stalling the photorespiratory salvage pathway and causing toxic phosphoglycolate accumulation.
- B.
Glycine decarboxylation in the peroxisome is directly inhibited, preventing the release of CO2 and NH3 required to maintain the Calvin cycle.
- C.
Protons rapidly accumulate in the mitochondrial matrix, reversing ATP synthase and depleting the cellular ATP required for the C2 cycle.
- D.
The chloroplast upregulates cyclic photophosphorylation to completely bypass the mitochondrial steps of the C2 cycle and directly convert glycolate to 3-PGA.
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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
Cytochrome_Oxidase|Proton_Gradient|ATP_Synthase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Location Trap: Students often memorize that photorespiration is a 'wasteful' process but fail to realize it is an essential salvage pathway to prevent phosphoglycolate toxicity.
The question tests the integration of mitochondrial ETC mechanics (NADH oxidation/PMF) with the C2 cycle, while heavily utilizing location traps (Peroxisome vs.
Mitochondria for glycine decarboxylation; Matrix vs.
Intermembrane space for proton accumulation).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Photorespiration Metabolic Cost |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |