Investigating enzymatic reactions

• Investigating the effect of pH on the rate of enzyme activity


  1. Put a drop of iodine solution into every well of a spotting tile

  2. Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 35 °C

  3. Use a syringe to add 1 cm of amylase solution and 1 cm of a buffer solution with a pH of 5 to a boiling tube. Put the tube into the beaker of water and wait for five minutes

  4. Use a different syringe to add 5 cm³ of a starch solution to the boiling tube

  5. Immediately mix the contents of the boiling tube and start a stop clock

  6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch

  7. Repeat the whole experiment with buffer solutions of different pH values

  8. Control any variables each time to make it a fair test
• Amylase


  Enzyme that catalyses the breakdown of starch to maltose
• Iodine solution


  Changes from browny-orange to blue-black in the presence of starch
• Spotting tile


  Used to hold drops of solution for testing
• Buffer solution


  Used to control the pH of the reaction mixture
• Dropping pipette


  Used to take samples from the reaction mixture
• Calculating the rate of reaction


  1. Divide the amount of product formed by the time taken

  2. Units are cm³/s or cm³ s
• Enzymes used in the digestive system


  • Amylase
  • Protease
  • Lipase
  • Sucrase
  • Maltase
• The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
• During an investigation into the activity of catalase, 24 cm³ of oxygen was released in 50 seconds
• You could easily adapt this experiment to investigate how factors other than pH affect the rate of amylase activity, such as temperature