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Procedure

1. Set up water baths at various temperatures (e.g. 0°C, 20°C, 40°C, 60°C and 80°C).
2. Add starch solution to 5 test tubes.
3. Add amylase solution to another 5 test tubes.
4. Place one starch and one amylase test tube into each water bath for 5 minutes - to allow the enzyme and substrate to reach the desired temperature.
5. Place 1 drop of iodine into each dimple on a spotting tile.
6. Add the amylase to the starch in the 0°C water bath.
7. Start the timer.
8. Every minute remove a sample of the starch-amylase solution and add it to a drop of iodine on the spotting tile.
9. Repeat step 8 until the iodine no longer changes colour - meaning that there is no starch present, in other words the amylase has broken all starch down.
10. Repeat steps 6-9 for each of the temperatures.
11. Record results.
12. Draw a graph to show the time taken for starch to be digested at different temperatures.

Results

At the optimum temperature the amylase will break down starch very quickly.

At low temperatures the amylase will break starch down slowly due to reduced kinetic energy.

At high temperatures the amylase will break starch down slowly or not at all due to denaturation of the enzyme’s active site.

Controlled variables

• pH
• Same volume and concentration of starch.
• Same volume and concentration of amylase.