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Question #47603
The Question
At elevated temperatures (>35°C), a C3 plant exhibits a sharp decline in net photosynthetic yield despite optimal light and water availability. Which of the following statements accurately describes the systemic metabolic failure occurring in the C3 plant compared to a C4 plant under identical conditions?
Options
- A.
Chemiosmotically generated ATP is utilized in the mitochondria to drive the release of CO2 during the conversion of glycine to serine.
- B.
RuBisCO binds with O2 to form one molecule of phosphoglycerate and one of phosphoglycolate, initiating a pathway that consumes ATP and releases CO2 without synthesizing sugars.
- C.
High temperatures denature RuBisCO in the mesophyll cells of the C3 plant, whereas the C4 plant protects its RuBisCO within the agranal chloroplasts of the bundle sheath.
- D.
Photorespiration is triggered, consuming ATP and NADPH in the peroxisome to salvage carbon, a process absent in C4 plants due to PEPcase's high oxygen affinity.
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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
RuBisCO|Chemiosmotic ATP Synthesis|C3 vs C4 Pathway
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The exact metabolic cost and location of events in Photorespiration.
Students often know photorespiration 'wastes ATP' and 'releases CO2', but fail to pinpoint the exact products of RuBisCO's oxygenase activity (1 PGA + 1 Phosphoglycolate) and falsely attribute ATP consumption to the mitochondria or peroxisome.
Furthermore, it tests the common misconception that PEPcase in C4 plants has a 'high' oxygen affinity, when in fact its evolutionary advantage is its complete lack of oxygenase activity.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Chemiosmotic ATP Synthesis Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |