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Question #45245
The Question
During a period of rapid vegetative growth, a plant cell extensively withdraws -ketoglutarate and succinyl-CoA from the Krebs cycle for the biosynthesis of amino acids and chlorophyll. Assuming this substrate depletion is not immediately balanced by anaplerotic (replenishing) reactions, which of the following will be the most direct consequence on mitochondrial respiration?
Options
- A.
A proportional decrease in the formation of metabolic water at the inner mitochondrial membrane due to reduced electron flux to oxygen.
- B.
An increase in the activity of Complex II (Succinate dehydrogenase) to maintain the proton motive force.
- C.
An increase in substrate-level phosphorylation within the mitochondrial matrix to compensate for reduced oxidative phosphorylation.
- D.
The respiratory pathway will become purely catabolic to restore the steady-state concentration of oxaloacetate.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Amphibolic Pathway|Metabolic Water Formation|Chemiosmotic ATP Yield
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the TCA cycle as a closed loop that strictly yields 3 NADH, 1 FADH2, and 1 ATP per turn.
The trap lies in failing to realize that its amphibolic nature means withdrawing intermediates breaks this stoichiometric yield.
Siphoning succinyl-CoA starves downstream enzymes, reducing ETC electron flux, collapsing the proton motive force, and ultimately decreasing metabolic water production.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Metabolic Flux and Steady State |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |