Lock and key model Induced and fit model

Chapter Enzymes | Lock & Key Model – Induced Fit Model

What Are Enzymes?

Enzymes are protein catalysts that speed up biochemical reactions by lowering the activation energy, while remaining unchanged themselves.

Lock & Key Model

Concept: The enzyme’s active site is a rigid, precisely shaped pocket into which only the matching substrate fits—like a key into a lock.

  • Substrate Specificity: High specificity due to complementary shapes.
  • Limitations: Does not account for flexibility or conformational changes.

Induced Fit Model

Concept: The enzyme’s active site is flexible and molds itself around the substrate upon binding, creating a more precise fit.

  • Dynamic Interaction: Conformational change stabilizes the transition state.
  • Enhanced Catalysis: Adjustments in shape optimize interactions and lower activation energy further.

Comparison of Models

FeatureLock & KeyInduced Fit
Active Site ShapeRigidFlexible
Substrate BindingExact complementarityConformational adjustment
Transition State StabilizationLimitedEnhanced
Model OriginEmil Fischer, 1894Daniel Koshland, 1958

Biological Significance

Understanding these models helps explain enzyme specificity, regulation, and mechanisms of inhibitors—critical for drug design and biotechnology applications.

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