effect of ph on amylase

• amylase breaks down starch molecules into simple sugars/glucose
• first step is to place one drop of iodine solution into each well of a spotting tile
• secondly, take 3 test tubes and in the first test tube add 2cm cubed of starch solution
• in the second test tube add 2cm cubed of amylase solution
• in the third test tube add 2cm cubed of ph 5 buffer solution
• buffer solutions are used to control the ph
• place all 3 test tubes in a water bath at 30 degrees and leave for 10 minutes to allow solutions to reach correct temperature
• next combine all three solutions into one test tube and mix using a stirring rod. return to the water bath and start a stopwatch
• after 30 seconds use the stirring rod to transfer one drop of solution to a well in the spotting tile which contains iodine.
• the iodine should turn blue-black showing that starch is present
• take a sample every 30 seconds and continue until iodine remains orange
• when iodine remains orange this tells us starch is no longer present and the reaction has completed
• repeat the whole experiment several times using different ph buffers for example ph 7,8,9
• a problem is we are only taking samples every 30 seconds which means we only have an approximate time for the reaction to complete. this can be addressed by taking samples every 10 seconds,
• another problem is that we are looking for a time when the iodine does not go blue-black and this is not always obvious as the colour change tends to be gradual so it can be difficult to see when the reaction has finished. ask several people to look at the spotting tile and decide wether the reaction has been completed.