effect of PH on amylase

• 1. place one drop of iodine solution into each well of a spotting tile ; why do we use iodine?

  to detect starch - if starch is present it turns blue or black.
• 2. take 3 test tubes

  in the first test tube add 2cm3 of starch solution.

  in the second test tube add 2cm3 of amylase solution.

  in the third test tube add 2cm3 PH 5 buffer solution ; why is buffer solution used?

  to control PH
• 3. place all test tubes in a water bath at 30C and leave for 10 minutes to allow the solutions to reach the right temperature.
• 4. combine the three solutions into one test tube and mix with a stirring rod. return to the waterbath and start a stop watch.
• 5. after 30 seconds, transfer one drop of solution to a well in the spotting tile using a stirring rod.
• what colour does the iodine solution turn if starch is present?

  blue-black
• 6. take a sample every thirty seconds until the iodine remains orange.
• what happens when the iodine remains orange?

  starch is no longer present
• repeat whole experiment several times using different PH buffers.
• problems in experiment;

  only taking samples every 30 seconds - we only have an approximate time for the reaction to complete. 


  address this by taking samples every ten seconds
• problems in experiment;

  it is not obvious when iodine does not go blue-black, colour change tends to be gradual .


  adress this is by asking several people to look at the spotting tile and decide when the reaction has completed.