Required Practical 05: Enzymes

Question 1

Describe how you would investigate the effect of pH on the rate of reaction of the amylase enzyme. (6)

Answer 1

1. Place starch solution, amylase solution and buffer solution in a water bath at 25°C for a few minutes.
2. Combine solutions and add a drop of the mixture to iodine solution on a tile.
3. Add the mixture to iodine solution drops on the tile at fixed 30s intervals until the iodine solution remains brown (does not turn blue-black).
4. Calculate the rate of reaction using 1 / time taken for solution to remain brown.
5. Repeat at different pH values using different buffer solutions.
6. Plot graph of rate (y) against pH (x).

Question 2

Which enzyme catalyses the breakdown of starch in the human digestive system?

Answer 2

Amylase - catalyses breakdown of starch to maltose.

Question 3

Why must samples be left in the water bath before solutions are mixed?

Answer 3

To allow temperature to equilibrate.

Question 4

What is a buffer solution?

Answer 4

A solution which can resist changes in pH.