Enzymes

• Enzymes are protein molecules that catalyse specific reactions in organisms.
• Catalyse means to speed up a reaction.
• Enzymes are specific because each enzyme only catalyses a specific reaction because the active site only fits together with certain substrates (like a lock and key).
• Amylase breaks down starch into simple sugars.
• Amylase is produced in the salivary glands, pancreas and small intestine.
• Protease breaks down proteins into amino acids.
• Protease is produced in the stomach, pancreas and small intestine.
• Lipase breaks down lipids into fatty acids and glycerol.
• Lipase is produced in the pancreas and small intestine.
• Temperature and pH affect the rate of activity of an enzyme.
• Denatured means 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.
• Describe the effect of temperature on enzyme activity:

  As temperature increases, rate of reaction increases until it reaches the optimum for enzyme activity - above this temperature, enzyme activity decreases and eventually stops.
• Describe the affect of pH on enzyme activity:

  different enzymes have different optimum pH at which their activity is greatest - at a pH much lower or higher than this, enzyme activity decreases and stops.
• Different digestive enzymes have different optimum pHs because 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.