Enzymes

• Enzyme

  A biological catalyst that speeds up reactions without being used up
• Enzyme functions

  1. Build larger molecules from smaller molecules by forming bonds

  2. Break down larger molecules into smaller molecules by breaking bonds
• Enzymes

  • They are proteins made up of long chains of amino acids
  • Each enzyme has a different shape due to the different amino acid chains
• Enzyme shape

  Extremely important for its function
• Enzyme action

  1. Enzymes have specific shapes

  2. Specific substrates can bind to an enzyme's active site
• Substrate

  The substance upon which an enzyme acts
• Active site

  The position on an enzyme by which a substrate can bind
• Enzyme-Substrate Complex


  The substrate binds to the enzyme's active site
• Lock and Key Hypothesis

  • Just like only one key can open a lock, only one type of enzyme can catalyse (speed up) a specific reaction
• Factors Affecting Enzymes


  • Temperature
  • pH
  • Substrate Concentration
  • Enzyme Concentration
• Effect of Temperature on Enzyme Catalase

  1. Low temperature: Low kinetic energy, less successful collisions between substrate and enzyme active site, slow rate of reaction

  2. Optimum temperature: More successful collisions, high rate of reaction

  3. High temperature: Active site changes shape, substrate no longer fits, enzyme has denatured, no reaction
• Decreasing pH


  Enzymes are beginning to denature
• Increasing pH


  Enzymes are beginning to denature
• As substrate concentration increases

  More enzyme-substrate complexes are formed, rate of reaction increases
• All enzymes' active sites are occupied


  This is the point of full saturation
• As enzyme concentration increases

  More enzyme-substrate complexes are formed
• Catalase is an enzyme in the liver that breaks down harmful hydrogen peroxide into oxygen and water
• Cooked liver exposed to very high temperatures

  Enzyme (catalase) has been denatured, active site changes shape, cannot break down the substrate
• Citric/acetic acid added to apple slice

  Decreased the pH, prevented the phenolase enzyme from catalysing the reaction, apple was not at its optimum pH, phenolase may have denatured, enzyme-substrate complexes cannot be formed
• Higher concentration of amylase enzyme

  More enzyme-substrate complexes can be formed, more products are formed, more starch is broken down, faster rate of reaction