Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
The activity of an enzyme was measured by varyin g the concentration of the substrate (S) in the
presence of three different concentrations of inhi bitor (I) 0, 2 and 4 mM.The double reciprocal plot
given belowsuggests that the inhibitor (I) exhibits
1/[S]
1/Vo
[I] = 0 mM
[I] = 2 mM
[I] = 4 mM
0
(A) substrate inhibition (B) uncompetitive inhibition
(C) mixed inhibition (D) competitive inhibition
Options:
(A) substrate inhibition
(B) uncompetitive inhibition
(C) mixed inhibition
(D) competitive inhibition
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2013 Q.34)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Systematic Conceptual & Option-by-Option Evaluation**:
- Problem Focus: *"The activity of an enzyme was measured by varyin g the concentration of the substrate (S) in the
presence of three different concentrations of inhi bitor (I) 0, 2 and 4 mM.The double reciprocal plot
given belowsuggests..."*
- **Option (D) [CORRECT]**: *"competitive inhibition"*
- Validated by canonical biochemistry/biotechnology literature. Specifically matches the molecular mechanism, kinetic model, or empirical finding required.
- **Option (A) [INCORRECT]**: *"substrate inhibition"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (B) [INCORRECT]**: *"uncompetitive inhibition"* does not satisfy the precise boundary conditions or molecular specificity.
- **Option (C) [INCORRECT]**: *"mixed inhibition"* does not satisfy the precise boundary conditions or molecular specificity.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **D**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.66 marks).
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