Computer Interfacing

Enzyme Action: Testing Catalase Activity

Teacher's Information

Suggestions and Tips

1. This experiment may take a single group several lab periods to complete. A good breaking point is after the completion of Step 17 of the procedure, when they have tested the effect of different enzyme concentrations. Alternatively, if time is limited, different groups can be assigned one of the three tests and the data can be shared.

2. You may want to supply pre-warmed temperature baths for Step 3 in Design New Experiments, where students need to maintain very warm water. Warn students not to touch the hot water.

3. Many different organisms may be used as a source of catalase in this experiment. If enzymes from an animal, a protist, and a plant are used by different teams in the same class, it will be possible to compare the similarities and differences among those organisms. Often, either beef liver, beef blood, or living yeast are used.

4. To prepare the yeast solution, dissolve 7 grams (1 package) of dried yeast for every 100 mL of 2% glucose solution. Incubate the suspension in 37-40°C water for at least 10 minutes to activate the yeast. Test the experiment before the students begin. The yeast may need to be diluted if the reaction occurs too rapidly. The reaction in Step 16, with 3 mL of 3% hydrogen peroxide, 3 mL of water, and 2 drops of suspension should produce a pressure of 1.3 atmospheres in 40 to 60 seconds.

5. To prepare a liver suspension, homogenize 0.5 to 1.5 g of beef liver in 100 mL of cold water. You will need to test the suspension before use, as its activity varies greatly depending on its freshness. Dilute the suspension until the reaction in Step 16 of the procedure, with 3 mL of 3% hydrogen peroxide, 3 mL of water, and 2 drops of suspension should produce a pressure of 1.3 atmospheres in 40 to 60 seconds. The color of the suspension will be a faint pink. Keep the suspension on ice until used in an experiment.

6. 3% H2O2 may be purchased from any supermarket. If refrigerated, bring it to room temperature before starting the experiment.

7. The Vernier Pressure Sensor may be used in place of the Biology Gas Pressure Sensor. Although it has less resolution than the Biology Gas Pressure Sensor, it has a greater range (0-6.8 atm).

8. The rubber stopper can be connected to the plastic tubing supplied with the pressure sensor as follows:

• A short length of glass tubing that is inserted into the rubber stopper can be drawn slightly out using a burner flame and fire polished.
• The thick-wall tubing supplied with the pressure sensor can then be easily connected to the tapered end of the glass tube.
• The other end of the tubing can fit into the nylon 3-way valve supplied with the newer pressure sensors.

9. Vernier Software sells a pH buffer package for preparing buffer solutions with pH values of 4, 6, 7, and 10. Simply add the capsule contents to 100 mL of distilled water. The order code is PHB.

You can also prepare pH buffers using the following recipes:

• pH 4.00: Add 2.0 mL of 0.1 M HCl to 1000 mL of 0.1 M potassium hydrogen phthalate.
• pH 7.00: Add 582 mL of 0.1 M NaOH to 1000 mL of 0.1 M potassium dihydrogen phosphate.
• pH 10.00: Add 214 mL of 0.1 M NaOH to 1000 mL of 0.05 M sodium bicarbonate.

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