4.3 (b) To investigate the effect of pH on the rate of
catalase activity
Teacher Notes
Apparatus required per class group of 24 students
Chopping board
12
Knife
12
Weigh boats
12
100 ml Graduated cylinders
36
Boiling tube
36
Syringe
12
Electronic balance
3
Dropper
12
Timer
12
Labels
36
Thermometer
12
Water bath
3
Enzyme source eg. Radishes/celery
Hydrogen peroxide
Range of buffer solutions
pH paper
Washing up liquid
Disposable gloves
The apparatus for this experiment lends itself to being pre-prepared in a ‘box of
equipment’ – see Section 1.
Advance preparation
o Prepare buffer solutions.
o Obtain fresh celery.
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Advance chemical preparation
(a) Hydrogen peroxide (Prepares 250 ml of 1M/’12 vol’ solution)
o Wearing gloves, measure out 29 ml of ‘100 vol’ hydrogen peroxide into a measuring
cylinder.
o Make up to 250 ml with water, add to a labelled bottle and mix well.
o Alternatively, small quantities of hydrogen peroxide can be purchased in the local
pharmacy.
Safety precautions
o Hydrogen peroxide is both oxidising and corrosive. For further information see
MSDS.
Expected outcome of experiment
o Catalase from celery has an optimum pH of 9. This buffer solution should result in
the greatest volume of foam produced.
o At pHs above and below 9 the activity of catalase decreases, less foam will be
produced.
Disposal and post-experiment work
o To dispose of hydrogen peroxide add small quantities (100 ml) in 10L of water and
run to foul water drain.
For the datalogging method for this experiment, please see Section 3.
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4.3 (b) To investigate the effect of pH on the rate of
catalase activity
Student Notes
Apparatus required per group
o Chopping board
o 3 x Labels
o Knife
o Thermometer
o Weight boat
o Trough
o 3 x Graduated cylinders
o Celery
o 3 x Boiling tubes
o Hydrogen peroxide
o Syringe
o Buffer solutions
o Electronic balance
o pH paper
o Dropper
o Washing-up liquid
o Timer
o Disposable gloves
Assembled apparatus
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Method
1. Add 20 ml of one of the selected buffers to a 100 ml graduated cylinder.
2. Using a dropper, add one drop of washing-up liquid to the cylinder.
3. Add 5 g of finely chopped celery to the cylinder.
4. Add 2 ml of hydrogen peroxide to a boiling tube.
5. Stand the cylinder and the boiling tube in the water bath at 25OC.
6. Pour the hydrogen peroxide into the cylinder.
7. Note the volume in the cylinder immediately and record.
8. Read the volume again after a measured amount of time, e.g. 2 minutes, and
record.
9. Subtract the initial volume from the final volume to get the volume of foam and
record.
10. Repeat the procedure from step 1 for each of the other buffer solutions.
11. A graph should be drawn of enzyme activity (volume of foam) against pH. Put pH
on the horizontal axis.
12. At the end of the experiment, clean all of the equipment and replace it in its
correct place.
Results:
pH of buffer
Initial volume
Final volume
Volume of
(ml)
(ml)
foam
produced (ml)
Conclusion/Comment
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