Catalase

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
Prepare buffer solutions.
Obtain fresh celery.

Advance chemical preparation
(a) Hydrogen peroxide (Prepares 250 ml of 1M/’12 vol’ solution)
Wearing gloves, measure out 29 ml of ‘100 vol’ hydrogen peroxide into a measuring cylinder.
Make up to 250 ml with water, add to a labelled bottle and mix well.
Alternatively, small quantities of hydrogen peroxide can be purchased in the local pharmacy.

Safety precautions
Hydrogen peroxide is both oxidising and corrosive. For further information see MSDS.

Expected outcome of experiment
Catalase from celery has an optimum pH of 9. This buffer solution should result in the greatest volume of foam produced.
At pHs above and below 9 the activity of catalase decreases, less foam will be produced.

Disposal and post-experiment work
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.

4.3 (b) To investigate the effect of pH on the rate of catalase activity

Student Notes

Apparatus required per group
Chopping board
Knife
Weight boat
3 x Graduated cylinders
3 x Boiling tubes
Syringe
Electronic balance
Dropper
Timer

3 x Labels
Thermometer
Trough
Celery
Hydrogen peroxide
Buffer solutions pH paper
Washing-up liquid
Disposable gloves

Assembled apparatus

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
(ml)
Final volume
(ml)
Volume of foam produced (ml)

Conclusion/Comment