Biology Enzymes SZABMU 2024 Reconduct
PMDC Verified Question 9 of 79
All of the following are the postulates of lock and key model, except:
A
Active site has a rigid structure
B
Enzymes are non-regulatory
C
One specific key can only open specific lock
D
Substrate combines with an enzyme to induce change in enzyme structure
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Substrate combines with an enzyme to induce change in enzyme structure
Concept:

The Lock and Key model is defined by absolute rigidity. Any mention of flexibility belongs to a different model.

Solution:

  • Postulates of Lock and Key: The active site is rigid (Option A). It fits only one specific substrate perfectly (Option C). Because of this rigidity, it cannot undergo complex allosteric regulation well (Option B).
  • However, Option D states the substrate induces a change in the enzyme structure. This is the exact, defining postulate of Koshland's Induced Fit Model, not Fischer's Lock and Key model.


Why other options are incorrect:

Options A, B, and C correctly describe the limitations and framework of the historical Lock and Key model. Option D is the only clear exception.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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