Factors Affecting Enzyme Action

• Enzyme

  Speeds up chemical reactions by having a groove on their surface called the active site
• Substrate

  The molecule that the enzyme reacts with, fits perfectly into the active site
• Lock and key theory


  The substrate must fit perfectly into the active site
• Effect of temperature on enzyme activity

  1. Gradually increase temperature

  2. Measure enzyme activity (rate of reaction)

  3. Activity increases as temperature increases

  4. Reach optimum temperature

  5. Activity rapidly decreases past optimum temperature
• Optimum temperature


  The temperature at which the enzyme is working at the fastest possible rate, maximum frequency of successful collisions between substrate and active site
• Denaturation

  At high temperatures, the enzyme molecule vibrates and the shape of the active site changes, so the substrate no longer fits perfectly
• Effect of pH on enzyme activity

  1. Alter pH

  2. Measure enzyme activity (rate of reaction)

  3. Enzyme has an optimum pH where activity is maximum

  4. Activity drops to zero if pH is too acidic or too alkaline
• Optimum pH


  The pH at which the enzyme works best
• Enzymes with different optimum pH

  • Protease enzyme in stomach (acidic pH)
  • Lipase enzyme from pancreas (alkaline pH)