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Question #45226
The Question
An enzyme extracted from a thermophilic bacterium (optimal temperature 80°C) is tested in vitro with a synthetic competitive inhibitor. At 30°C, the inhibitor successfully binds to the active site and halts enzyme activity. However, at 80°C, the enzyme efficiently catalyzes its natural substrate, and the inhibitor shows almost no effect despite being present in equal concentration. Assuming the inhibitor molecule itself is thermally stable, which of the following best explains this phenomenon?
Options
- A.
The enzyme undergoes irreversible denaturation at 80°C, altering the active site geometry so the inhibitor can no longer bind.
- B.
High temperatures alter the primary structure of the apoenzyme, permanently disrupting the thermodynamic stability of the enzyme-inhibitor complex.
- C.
At 80°C, the enzyme achieves its optimal tertiary conformation, which maximizes substrate affinity but structurally reduces the binding affinity of the inhibitor.
- D.
The competitive inhibitor binds covalently at 80°C, converting into an allosteric modulator that decreases the Vmax of the reaction.
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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
Competitive Enzyme Inhibition Kinetics|Protein Denaturation Specificity|Thermal Tolerance Ranges
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often blindly associate 'high temperature' with 'enzyme denaturation' (Option A trap) without accounting for the extremophile context.
Furthermore, it tests the advanced understanding that competitive inhibition relies on precise structural mimicry; a temperature-induced conformational shift in the apoenzyme's tertiary structure can alter binding affinity for an inhibitor without destroying the enzyme's structural integrity for its natural substrate.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Competitive Enzyme Inhibition Kinetics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |