8.5 Enzyme Activity
1. Experimental Considerations
Catalase is an enzyme found in plants and animals which
breaks down hydrogen peroxide:
hydrogen peroxide
water + oxygen
The aim of the experiment is to investigate the effect of pH
on the activity of the enzyme catalase.
Potato contains catalase and so can be used in the
experiment below to measure the enzyme activity.
The activity of the enzyme is measured by counting the
number of oxygen bubbles produced.
Variables which should be kept constant include the:
 size of the potato pieces
 volume of the hydrogen peroxide
 concentration of the hydrogen peroxide
2. Effect of pH
Method:





the apparatus was set up as shown.
5cm3 of pH 7 solution was added to the test tube.
4 potato disks were also added to the test tube.
the mixture was left to stand for 2 minutes.
after this time 5 cm3 of hydrogen peroxide was added
to the test tube
 the stopper with delivery tube was inserted and the
timer started.
 the number of bubbles produced was counted over a 3
minute period.
 the experiment was repeated using fresh potato and
solutions of different pH.
Results:
pH of solution
Number of oxygen bubbles
In 3 minutes
1
4
7
10
13
0
6
28
63
45
Graph of Results:
70
Number of
oxygen
bubbles
60
50
40
30
20
10
0
0
2
4
6
8
10
12
14
pH of Solution
Conclusion:
The activity of catalase increases with pH to an optimum
pH of 10. Thereafter, the activity decreases with increasing
pH.
3. Effect of Temperature
This activity examines the effect of temperature on the activity of the
enzyme catalase.
Method:
The previous experiment was repeated at pH 7.
Instead of altering the pH, the temperature was changed.
Graph of results:
25
Number of
bubbles
20
15
10
5
0
0
20
40
60
80
Temperature (˚C)
Conclusion:
The activity of the enzyme increases with temperature up
to the optimum temperature of 40˚C. Thereafter, the
activity drops off very quickly to zero with increasing
temperature.