Effects of pH on Amylase

• What is Amylase?


  An enzyme.
• What does Amylase do?

  Breaks down starch molecules into simple sugars
• What is Step 1 of the Amylase practical?

  Place one drop of iodine solution into each well of a spotting tile.
• Why do we use Iodine solution?

  Iodine tests for Starch and goes blue-black if it is present
• What is Step 2 of the Amylase practical?


  Take three test tubes and label each one with a letter (e.g. A,B,C)
• What goes into Test Tube A?


  2 cm cubed of starch solution
• What goes into Test Tube B?


  2 cm cubed of Amylase solution
• What goes into Test Tube C?


  2 cm cubed of a pH 5 buffer solution
• What goes into Test Tube B?

  2 cm cubed of Amylase solution
• Why are buffer solutions used in Biology?


  To control the pH
• What is Step 3 of the Amylase practical?

  Place all 3 test tubes in a water bath at 30 degrees celsius and leave them for 10 minutes.
• Why do we put the tubes into a water bath?


  So all solutions reach a correct, equal temperature
• What is Step 4 of the Amylase practical?

  Combine all three solutions into one test tube and mix with a stirring rod.

  Then immediately return the new test tube to the water bath and begin a stopwatch.
• What is Step 5 of the Amylase practical?

  After 30 seconds, use the stirring rod to transfer one drop of solution to a well in the spotting tile which contains iodine.
• What colour should the iodine in the first well go as starch should be present?

  Blue-black
• What is Step 6 of the Amylase practical?

  Continue taking a sample every 30 seconds until the iodine remains orangey-brown.
• What does the iodine remaining orangey-brown tell us?


  Starch is no longer present and the reaction has completed
• What should we record?


  The time taken for the reaction to be completed
• What is the final step of the Amylase practical?


  Repeat the whole experiment several times using different pH buffers (e.g. ph 7, pH 8 and pH 9)
• What is a problem with the Amylase practical?

  We are only taking a sample every 30 seconds meaning we only get an approximate time for the reaction to complete.
• How do we address this problem in the Amylase practical?

  Take a sample more frequently (e.g every 10 seconds)
• What is another problem with the Amylase practical and how can we address it?

  We are looking for the time that the iodine does not go blue-black and this is not always obvious as the colour change can be gradual so it can be difficult to tell when the reaction has completed.

  To address this we can ask several people to look at the spotting tile and decide when the reaction has completed.