Before You Begin
Question #47643
The Question
During a state of low cellular ATP demand, a high NADH/NAD⁺ ratio allosterically inhibits the enzyme isocitrate dehydrogenase in the mitochondrial matrix. Based on the amphibolic nature of the respiratory pathway, how is the resulting accumulated intermediate primarily rerouted?
Options
- A.
Citrate is exported to the cytosol and cleaved to form Acetyl-CoA for fatty acid synthesis.
- B.
α-ketoglutarate is withdrawn from the matrix to synthesize amino acids like glutamate.
- C.
Succinyl-CoA is diverted to the cytosol to synthesize cytochrome pigments.
- D.
Oxaloacetate is continuously converted to malate to maintain the proton motive force.
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
TCA Cycle|NADH Dehydrogenase|Proton Pumping
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Understanding metabolic flux and enzyme inhibition.
Students often memorize that the TCA cycle is amphibolic and provides various precursors (like Succinyl-CoA for cytochromes or α-KG for amino acids).
However, the trap lies in applying the logic of 'where' the cycle stalls.
Inhibition of isocitrate dehydrogenase causes upstream accumulation (Citrate) and downstream depletion (α-KG, Succinyl-CoA), making Option A the only metabolically viable rerouting event under these specific high-energy conditions.
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 |