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Question #47624
The Question
A researcher is studying a transgenic C_4 plant engineered to express a highly thermostable RuBisCO (analogous to Taq polymerase) to maximize carbon fixation at extreme temperatures (45°C+). During the experiment, a specific chemical inhibitor is applied that selectively blocks cyclic photophosphorylation in the plant's chloroplasts. What will be the most immediate and direct metabolic consequence of this inhibition on the C_4 pathway?
Options
- A.
Accumulation of malic acid in the bundle sheath cells due to the failure of the ATP-dependent decarboxylation step.
- B.
Failure of PEP regeneration in mesophyll cells, leading to a drop in bundle sheath CO_2 concentration and the initiation of photorespiration.
- C.
Complete cessation of the Calvin cycle in the mesophyll cells due to a critical lack of ATP for RuBP regeneration.
- D.
Increased efficiency of the C_4 pathway as the plant shifts entirely to non-cyclic photophosphorylation to meet its energy demands.
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
ATP_Requirement|Bundle_Sheath_Cells|Taq_Polymerase_Heat_Tolerance
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'C_4 plants lack photorespiration' as an absolute rule, forgetting it is a conditional state maintained by an ATP-expensive CO_2 pump.
The trap tests the understanding that Kranz anatomy alone cannot prevent photorespiration if the thermodynamic cost (ATP from cyclic photophosphorylation) of PEP regeneration in the mesophyll is not met.
It also utilizes a 'Location Trap' (Option C) by misplacing the Calvin cycle in mesophyll cells.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | C4 Pathway Efficiency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |