Enzymes

• Substrate


  The substance an enzyme breaks down
• Enzyme


  A biological catalyst that speeds up the rate of a biological reaction without being used up in the reaction itself
• Catalase


  • An enzyme found concentrated in mammalian livers
  • It catalyses (breaks down) poisonous hydrogen peroxide into harmless water and oxygen
• Reaction catalysed by Catalase

  1. Hydrogen peroxide

  2. Water

  3. Oxygen
• Our cells are always making poisonous chemicals, but do not die because the cells use enzymes to break down the poisonous chemicals into harmless substances
• Enzyme active site


  An indent in the enzyme where the substrate fits
• Enzyme and substrate


  The substrate fits into the active site of the enzyme
• Enzyme catalysis


  1. Enzyme and substrate join together

  2. Substrate is broken down into products

  3. Enzyme is unchanged and can be used again
• Enzyme specificity


  An enzyme only breaks down one specific type of substrate molecule
• Lock and key model


  The shape of the active site and the substrate are complementary (mirror images) to each other
• Enzymes lower the energy needed for biological reactions to take place
• Temperature, pH and enzyme concentration all affect the action of enzymes
• The maximum rate of enzyme activity is described as the optimum