3️⃣PAG 4: Rates of enzyme controlled reactions

Question 1

Safety (2)

Answer 1

use eye protection.
Iodine is harmful, avoid contact with skin.

Hydrogen peroxide is an irritant, wear safety goggles when handling and avoid contact with skin. Take care when handling the sharp cork borer and scalpel.

Question 2

Equipment

Answer 2

• amylase solution (0.5%)
• iodine solution in a dropper bottle
• 5 cm3 syringes
• test-tube rack
• spotting tile
• marker pen or chinagraph pencil • starch solution (0.5%)
• buffer solutions covering a range of pH values
• pipette
• test tubes (one for each pH to be tested)
• stop clock
• water baths set at 30C

Question 3

Amylase is an example of a __ enzyme. It catalyses the breakdown of __ into __ in your __ and your __ __. This reaction is pH dependent.
You can test for starch using __ indicator. If starch is present it will change from an __ colour to a ___ colour.
The following method can be used to investigate how pH affects the rate amylase catalyses the breakdown of starch. You should alter this method appropriately if you wish to investigate another factor.

Answer 3

Amylase is an example of a carbohydrase enzyme. It catalyses the breakdown of starch into glucose in your mouth and your small intestine. This reaction is pH dependent.
You can test for starch using iodine indicator. If starch is present it will change from an orange colour to a dark blue/black colour.
The following method can be used to investigate how pH affects the rate amylase catalyses the breakdown of starch. You should alter this method appropriately if you wish to investigate another factor.

Question 4

Method (10 steps)

Answer 4

1 Use the syringe to place 2 cm3 of amylase solution into a test tube.
2 Use another syringe to add 1 cm3 of pH buffer solution to the test tube.
3 Place the test tube into a water bath set at 30 C and leave for 5 minutes
4 Whilst waiting, add a drop of iodine solution into each dimple of a spotting tile.
5 After 5 minutes, use another syringe to add 2 cm3 of starch to the amylase/ buffer solution, start the stop clock and leave it on throughout the test. Mix using a plastic pipette.
6 Remove a drop of amylase/starch/buffer mixture after 10 seconds and add to the first drop of iodine on your spotting tile.
7 Wait another 10 seconds. Then remove a second drop of the mixture to add to the next drop of iodine.
8 Repeat step 6 until the iodine solution and the amylase/buffer/starch mixture remains orange.
9 Record the time taken for the amylase to fully digest the starch.
10 Repeat the whole procedure with a different pH buffer.

Question 5

Results (2)

Answer 5

You will need to calculate the rate of reaction for each value of your independent variable.
Design a suitable results table to record your results.

Question 6

Controlled varibales (4)

Answer 6

● Temperature
● pH
● Time for gas collection?/??
● Length of potato cylinder?”