GCSE Combined Science (AQA)

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Lock & Key Theory

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Organisation Animal Tissues, Organs and Organ Systems

Lock & Key Theory

1:50 Digestion
Spec 4.2.2.1
Previous Digestive Enzymes Next Carbohydrates & Carbohydrases
  • The Lock and Key theory explains enzyme specificity, comparing enzymes to locks and substrates to keys.
  • Enzymes are specific to their substrates due to the unique shape of their active sites.
  • Different enzymes catalyze specific reactions; digestive enzymes break down substrates, while synthesis enzymes join molecules.
  • The active site of an enzyme is complementary to the shape of its substrate, allowing the substrate to fit neatly.
  • If the active site is not complementary to the substrate, the substrate will not bind, preventing the enzyme from facilitating the reaction.
  • Models demonstrating this concept are useful for explaining enzyme action in exams.

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