Computer Interfacing

Enzyme Action: Testing Catalase Activity

Procedure

1. Obtain and wear goggles.

2. Prepare the pressure sensor for data collection:

• Plug the pressure sensor into Port 1 of the Serial Box Interface or ULI.
• Attach the heavy-wall plastic tubing of the rubber-stopper assembly to the end opening of the 3-way valve of the Pressure Sensor.

3. Prepare the computer for data collection.

4. Leave the side valve of the pressure sensor open until Step 10.

If your pressure sensor has a plastic valve, align the blue handle with the arm that leads to the pressure sensor.

Test the Effect of Enzyme Concentration

5. Place four test tubes in a rack and label them 1, 2, 3, and 4 Drops. Partially fill a beaker with tap water for use in Step 6.

6. Add 3 mL of water and 3 mL of 3% H2O2 to each of the four test tubes.

7. Using a clean dropper pipette, add 1 drop of enzyme suspension to the test tube labeled 1 Drop. Note: Be sure not to let the enzyme fall against the side of the test tube.

8. Insert the 1-hole stopper assembly into the test tube. Note: Firmly twist the stopper for an airtight fit.

9. Shake or flick the tube to thoroughly mix its contents. The reaction should begin. The next two steps should be completed as rapidly as possible.

10. Close the air valve on the pressure sensor. Align the blue handle with the side stem.

11. Start measuring the pressure by clicking on the Start button.

12. If you do not manually stop the program, data collection will end after 3 minutes. If the pressure exceeds 1.3 atmospheres, the pressure inside the tube will be too great and the rubber stopper is likely to pop off. If the pressure exceeds 1.3 atmospheres:

• Stop the data collection by clicking on the Stop button.
• Open the air valve on the pressure sensor.

13. After the computer stops, save your data as directed by your instructor.

14. Find the rate of enzyme activity.

15. Add 2 drops of the enzyme solution to Test Tube 2. Repeat Steps 8-14.

16. Add 3 drops of the enzyme solution to Test Tube 3. Repeat Steps 8-14.

17. Add 4 drops of the enzyme solution to Test Tube 4. Repeat Steps 8-14.

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