CORE PRACTICAL: 2: Investigating the effect of pH on enzyme activity

Question 1

method: (11 steps)

Answer 1

1- Set up: bunsen burner, heatproof mat, tripod and gauze.
2- Place beaker of water on gauze and adjust flame to keep the water at about 35°C.
3- put two drops of iodine solution into each spot of spotting tile.
4- Add 2 cm³ of amylase enzyme solution to a test tube.
5- Place 2 cm³ of starch solution into the same tube.
6- add 1 cm³ of pH solution to the tube. (this will keep the pH constant)
7- Mix solution in test tube and place it into beaker of water on Bunsen burner.
8- Use pipette to remove few drops of solution every 20 seconds from test tube and put them into a different well of the spotting tile.
9- Repeat until iodine solution stops turning black.
10- Record the time this takes.
11- Repeat with different pH solutions.

Question 2

risks: (2)

Answer 2

• Iodine solution is an irritant. (If it touches skin it should be washed off)
• Goggles should be worn at all times.

Question 3

conclusion: (4)

Answer 3

• enzyme amylase breaks down starch into glucose.
• If the enzyme is working effectively, this will happen quickly.
• At pH 7 it took the shortest time before the iodine no longer changed colour.
• This shows that the starch was broken down more quickly at this pH. The optimum pH for amylase is therefore pH 7.