Required practical 5 - Enzymes

Question 1

Describe how you would investigate the effect of pH on the rate of reaction of the amylase enzyme

Answer 1

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

Question 2

What enzymes catalyses the breakdown of starch in the human digestive system?

Answer 2

Amylase - catalyses breakdown of starch into 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.