Enzyme Investigations (CIE IGCSE Biology: Co-ordinated Sciences (Double Award))

• Starch solution is heated to a set temperature
• Iodine is added to wells of a spotting tile
• Amylase is added to the starch solution and mixed well
• Every minute, droplets of solution are added to a new well of iodine solution
• This is continued until the iodine stops turning blue-black (this means there is no more starch left in the solution as the amylase has broken it all down)
• Time taken for the reaction to be completed is recorded
• Experiment is repeated at different temperatures
• The quicker the reaction is completed, the faster the enzyme is working

Investigating the effect of temperature on enzyme activity

• Place single drops of iodine solution in rows on the tile
• Label a test tube with the pH to be tested
• Use the syringe to place 2cm³ of amylase in the test tube
• Add 1cm³ of buffer solution to the test tube using a syringe
• Use another test tube to add 2cm³ of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing using a pipette
• After 10 seconds, use a pipette to place one drop of mixture on the first drop of iodine, which should turn blue-black
• Wait another 10 seconds and place another drop of mixture  on the second drop of iodine
• Repeat every 10 seconds until iodine solution remains orange-brown
• Repeat experiment at different pH values - the less time the iodine solution takes to remain orange-brown, the quicker all the starch has been digested and so the better the enzyme works at that pH

Investigating the effect of pH on enzyme activity