Enzyme Catalysis

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•  Enzyme catalysis involves molecular motion and the collision of substrates with the active site

Enzyme reactions typically occur in aqueous solutions (e.g. cytoplasm, interstitial fluid, etc.)

  • Consequently, the substrate and enzyme are usually moving randomly within the solution (Brownian motion)
  • Sometimes an enzyme may be fixed in position (e.g. membrane-bound) – this serves to localise reactions to particular sites

Enzyme Catalysis

Enzyme catalysis requires that the substrate be brought into close physical proximity with the active site

  • When a substrate binds to the enzyme’s active site, an enzyme-substrate complex is formed
  • The enzyme catalyses the conversion of the substrate into product, creating an enzyme-product complex
  • The enzyme and product then dissociate – as the enzyme was not consumed, it can continue to catalyse further reactions 

Enzyme-Substrate Interactions


Collision Frequency

The rate of enzyme catalysis can be increased by improving the frequency of collisions via:

  • Increasing the molecular motion of the particles (thermal energy can be introduced to increase kinetic energy)
  • Increasing the concentration of particles (either substrate or enzyme concentrations)

Summary of Enzyme-Substrate Kinetics

Link:  Enzyme Catalysis Simulation