Enzyme

• DOXI


  Digestive enzymes
• Digestive


  Molecules that can then be absorbed into the bloodstream
• These products of digestion can be used to build new carbohydrates, lipids, and proteins
• Some of the glucose produced is used in respiration
• Enzymes


  • amylase
  • proteases
  • lipase
• amylase


  • Sites of production: salivary glands, pancreas, small intestine
  • Reaction catalysed: starch to simple sugars
• proteases


  • Sites of production: stomach, pancreas, small intestine
  • Reaction catalysed: proteins to amino acids
• lipase


  • Sites of production: pancreas, small intestine
  • Reaction catalysed: lipids to fatty acids and glycerol
• pH


  Measure of acidity or basicity
• Different enzymes have different optimum pH values
• This allows enzymes to be adapted to work well in environments with different pH values
• Parts of the digestive system differ greatly in pH, so the enzymes that work there have different optimum pH values
• Enzyme optimum pH


  Protease in stomach acid, amylase in neutral saliva
• Effect of temperature on enzymes

  • As temperature increases, rate of reaction increases because enzyme and substrate molecules move around faster and collide more frequently
  • Optimum temperature is when the reaction works as fast as possible
  • At very high temperatures, the enzyme is denatured and stops working
• Denaturation


  At extremes of pH or very high temperatures, the shape of an enzyme's active site can change, so the substrate can no longer bind and the enzyme cannot catalyse the reaction
• The substrate no longer fits into the active site, so the enzyme has been denatured
• Plant meristems


  Areas where rapid cell division occurs in the roots and shoots
• This practical tests your ability to accurately measure and record time, temperature, volume, and pH
• You need to be able to apply the methods of this practical to different enzymes and substrates
• The optimal pH of amylase is around 7, so the time taken to break down starch will be shortest at pH 7
• At pH values lower than 7 it will take longer to break down the starch - it will take the longest time at pH 5, decreasing in time taken until pH 7
• Above pH 7 it will take a longer time to break down the starch, and the amylase may stop breaking down the starch entirely at pH 11
• Using the same enzyme solution on two different days would not give comparable results