Required Praticle: Effect of PH on Amylase Flashcards
Why do we use iodine?
- To test the presence of starch.
- Iodine turns blue/black if starch is present.
Method: Steps 1-2.
1) Place one drop of iodine solution into each well of a spotting tile.
2) Take 3 test tubes and:
1st test tube: 2cm^3 of starch solution.
2nd test tube: 2cm^3 of Amylase solution/
3rd test tube: 2cm^3 of pH 5 buffer solution.
(Why is buffer solution used for? To control the PH). `
Methods: Steps 3-4.
3) Place all 3 test tubes in a water bath at 30 degrees celcius.
- Leave them for 10 minutes to allow the solutions to reach the correct temperature.
4) Combine the 3 solutions into 1 test tube and mix with a stirring rod. Return to the water bath and start a stop watch.
Methods Steps 4-5
4) After 30 seconds: Use the stirring rod to transfer one drop of iodine solution to a well in a spotting tile which contains iodine.
5) Iodine should turn black and blue to show starch is present.
6) Take a sample every 30 seconds and we continue until the iodine remains orange.
What does it show when the iodine remains orange?
- Starch is no longer present.
- Reaction has been completed.
- Record the time for this on our results.
Last step?
- Repeat the whole experiment several times using different Ph buffers.
What are the problems for this practical?
- Taking samples every 30 seconds: Approximation reaction time. Instead take samples every 10 seconds.
2) Looking for the time for the iodine to not change from orange is not obvious. Colour change is gradual as some iodine may have black blue and orange so it is difficult to tell.
- Ask several people to look at the spotting tile + decide when reaction is competed.
