B3 Enzymes Practical


Materials needed

  • 10 test tubes 
  • a test tube rack 
  • a water bath 
  • a thermometer 
  • a spotting tile 
  • a 5 cm3 measuring cylinder 
  • pasteur pipettes 
  • a glass rod
  • a stopclock 
  • starch solution 
  • amylase solution 
  • iodine solution 
  • labelled buffered solutions at a range of pH values 
  • labels.
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Method - Preparing the Experiment

  • Heat your water bath to 35 °C. 
  • Put 2 cm3 of each buffered solution into individual, separate test tubes. Label each tube with the pH of the solution.
  • Label 5 test tubes ‘Starch’ and add 4 cm3 of starch solution into each tube.
  • Put a thermometer in one of the starch test tubes to monitor the temperature. Leave the thermometer in this tube throughout the experiment.
  • Add 10 cm3 of Amylase solution into another test tube. Label the tube ‘amylase’.
  • Put all the test tubes into the water bath.
  • Allow the solutions to reach 35 °C.
  • While the solutions are reaching the required temperature, put one drop of Iodine solution into each depression on your spotting tile. 
  • Put a drop of starch solution in the first depression of the tile. This is the result at 0 time. It is used as a comparison for the other solutions. 
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Method - Carrying Out the Experiment

  • When all the tubes have reached 35 °C take one of the tubes of starch from the water bath and add the 2 cm3 of your first pH buffered solution. Stir the mixture with a glass rod.
  • Use the pipette to add 2 cm3 of amylase solution to the mixture. Start the stopclock as soon as you add the amylase. Stir with the glass rod. 
  • After 10 seconds, remove one drop of the mixture with a glass rod.
  • Put this drop on the second depression of your spotting tile. 
  • Every 10 seconds, use the glass rod to remove one drop of the mixture. Put each drop onto the iodine solution in the next depression on the spotting tile. Remember to rinse the glass rod with water after putting each drop on the spotting tile.
  • Keep sampling every 10 seconds until the iodine does not change colour.
  • Record your results in a table. 

Repeat with the other pH buffered solutions. 

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