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Question #47645
The Question
Photorespiration acts as a severe metabolic drain on C3 plants, consuming the ATP and NADPH generated by the thylakoid proton gradient without yielding net carbon fixation. Which of the following statements regarding this process and its evolutionary bypass in C4 plants is INCORRECT?
Options
- A.
Under high temperature, an increased O2/CO2 ratio in C3 plants causes Rubisco to split RuBP into one molecule of 3-phosphoglycerate and one molecule of phosphoglycolate.
- B.
The C4 pathway prevents this energy drain by utilizing ATP in the mesophyll cells to regenerate PEP, effectively acting as a CO2-concentrating mechanism.
- C.
During the photorespiratory salvage pathway in C3 plants, the decarboxylation step that releases previously fixed carbon as CO2 occurs within the peroxisome.
- D.
The bundle sheath cells of C4 plants possess thick walls impervious to gaseous exchange, which helps maintain the high CO2 concentration generated by malic acid decarboxylation.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Chloroplast|Peroxisome|Mitochondrion
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Location Trap: Students often memorize the three organelles involved in photorespiration (Chloroplast, Peroxisome, Mitochondrion) but fail to map the specific biochemical events to their exact locations.
The trap exploits the assumption that because the peroxisome is the intermediate organelle heavily involved in oxidation, it might also be the site of CO2 release.
Furthermore, it tests the precise NCERT phrasing regarding Kranz anatomy ('impervious to gaseous exchange') and Rubisco's exact cleavage products.
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 |