RP12

• Core Practical 12


  Investigate the effect of temperature on the rate of an enzyme-catalysed reaction, to include Q10
• Factors affecting rate of enzyme-catalysed reaction

  • Temperature
  • pH
  • Concentration of substrate
  • Concentration of enzyme
• Determining effect of factors

  1. Changing a single variable

  2. Measuring its effect on rate of reaction

  3. Keeping all other variables constant
• Initial rate of reaction

  Measured because rate of enzyme-controlled reaction is high, as enzymes act as biological catalysts, so concentration of reactants changes rapidly
• Initial rate is the only point during the reaction when concentration of reactants and products is known
• Temperature coefficient (Q10)


  Indicates the change in rate of reaction caused by a 10 degree increase in temperature, calculated by dividing rate of reaction at temperature T + 10 degrees by rate of reaction at temperature T
• Q10 can only be used up to optimum temperature
• Q10 for catalase is about 2, the rate doubles for every 10 degree increase
• Equipment


  • Water bath
  • Boiling tube
  • Bung
  • Soaked peas
  • Hydrogen peroxide solution
  • Delivery tube
  • Gas syringe
  • Stop clock
  • Mortar and pestle
• Method


  1. Grind a known mass of peas in distilled water

  2. Add 5cm of hydrogen peroxide solution to the peas

  3. Fit the syringe into a delivery tube and the delivery tube into the boiling tube with a bung

  4. Place the boiling tube into a water bath at a known temperature

  5. Time for a set length of time e.g. 5 minutes, measure the volume of gas produced at regular intervals e.g. 30 seconds

  6. Repeat the experiment at different temperatures
• Hazards


  • Biohazard contamination
  • Broken glass
  • Hot liquids
  • Hydrogen peroxide
• Safety precautions


  • Use disinfectant, wash hands with soap after handling
  • Take care when handling glassware, keep away from edge of desk
  • Handle with care, use tongs to remove boiling tubes from water bath, wear eye protection, keep away from edge of desk
  • Wear eye protection, avoid contact with skin
• In emergency


  • Seek assistance
  • Elevate cuts, apply pressure, do not remove glass from wound, seek medical assistance
  • Run burn under cold water, seek medical assistance
  • Wash off skin immediately, flood eye/cuts with cold water
• Graph


  Plot a graph of temperature against ethanol concentration/temperature
• Conclusion


  1. Rate can be calculated by dividing volume of gas produced by time

  2. Q10 can be calculated by dividing rate at T+10 degrees by rate at T degrees