Biology Enzymes PMC 2020
PMDC Verified Question 59 of 79
Lock and key model for enzyme action proposed by Emil Fischer suggests that:
A
Enzyme can catalyze variety of reactions
B
Enzymes can modify their active sites
C
Enzymes are unbiased for substrate
D
Enzymes are restricted to one reaction type
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Enzymes are restricted to one reaction type
Concept:

The Lock and Key model implies absolute rigidity and absolute specificity.

Solution:

  • Proposed by Emil Fischer in 1894, this model states that an enzyme's active site perfectly matches the shape of only one specific substrate, much like a specific key fits only one lock.
  • Because of this rigid and highly specific physical match, the enzyme is entirely restricted to catalyzing one single, specific type of reaction.


Why other options are incorrect:

The ability to modify active sites belongs to the Induced Fit model. Catalyzing a variety of reactions contradicts the core premise of absolute specificity in the Lock and Key model.

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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