Core Practical 4

• What factors influence the rate of an enzyme-controlled reaction?

  Temperature, pH, substrate concentration, enzyme concentration
• How can the effect of each factor on the rate of reaction be determined?

  By changing a single variable and measuring its effect
• Why is it important to keep all other variables constant during the experiment?

  To prevent them from influencing the results
• When is the initial rate of reaction measured?

  When concentration of reactants and products is known
• Why is the initial rate of reaction high in enzyme-controlled reactions?

  Because enzymes act as biological catalysts
• What is the initial rate of reaction in enzyme-controlled reactions?

  The only point when concentrations are known
• What equipment is needed for the enzyme experiment?

  • Milk powder solution
  • Trypsin solution (1%)
  • Test tubes
  • Test tube holder
  • Stopclock
  • 5cm​3​ pipettes
  • Goggles
  • Colorimeter
  • Cuvettes
  • Distilled water
• How should the stock solution of trypsin be prepared?

  By diluting with distilled water to specific concentrations
• What is the purpose of the control in the experiment?

  To set the colorimeter absorbance to zero
• How often should absorbance be measured during the experiment?

  At 15 second intervals for 5 minutes
• What should be done after measuring absorbance in the cuvette?

  Rinse the cuvette with distilled water
• What are the risks associated with the experiment and their precautions?

  • Broken glass: Handle carefully, seek medical help if injured
  • Hot liquids: Use tongs, run burns under cold water
  • Enzymes: Avoid contact, wear eye protection
• What should be plotted on the graph in the experiment?

  Rate of reaction against temperature
• What happens to milk when casein is broken down by trypsin?

  • Milk turns colorless
  • Casein is hydrolyzed by trypsin
• How does increasing trypsin concentration affect enzyme-substrate complexes?

  It increases the number of complexes forming
• What happens to the rate of reaction as enzyme concentration increases?

  It increases up to the optimum concentration
• What occurs when all substrates occupy an active site?

  The rate plateaus and does not increase
• How can the procedure be modified to measure substrate concentration effects?

  • Dilute milk suspension for different concentrations
  • Control concentration of trypsin
• What is trypsin classified as?

  A protease enzyme
• What is the role of trypsin in the experiment?

  To hydrolyze casein in milk