B5 Enzymes

• Enzymes are protein molecules that catalyse specific reactions in organisms
• Enzyme specificity


  Each enzyme only catalyses a specific reaction, because the active site only fits together with certain substrates (like a lock and key)
• Amylase function


  To break down starch into glucose
• Amylase is produced in the salivary glands, pancreas, and small intestine
• Protease function


  To break down proteins into amino acids
• Proteases are produced in the stomach, pancreas, and small intestine
• Lipase function


  To break down lipids into fatty acids and glycerol
• Lipases are produced in the pancreas and small intestine
• Factors affecting enzyme activity


  • Temperature
  • pH
• Denaturation


  The shape of an enzyme's active site is changed by high temperatures or an extreme pH, so it can no longer bind with the substrate
• As temperature increases


  Rate of reaction increases until it reaches the optimum for enzyme activity, then decreases and eventually stops
• Optimum pH


  Different enzymes have a different optimum pH at which their activity is greatest - a pH much lower or higher than this enzyme activity decreases and stops
• Different parts of the digestive system have very different pHs - the stomach is strongly acidic, and the pH in the small intestine is close to neutral
• When the active site breaks down, an enzyme becomes denatured - this is not the same as the enzyme dying or being killed