GCSE Biology (Edexcel)

Topic Summaries

Human health and enzymes

Lock and key theory

  • Enzymes catalyse (speed up) specific reactions in organisms due to the shape of their active site.
  • The substrate is the reactants of the reaction to be catalysed.
  • The ‘lock and key theory’ proposes that the shape of the substrate is complementary to the active site so can bind to it, which allows the enzyme to break the bonds holding the substrate together.
  • Enzyme-catalysed reactions contribute to metabolism.

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