SBI4U
Factors Influencing Enzyme Activity
Introduction:
Enzymes act as specific catalysts for chemical reactions in living cells, by lowering the
activation energy required for a reaction to occur. The enzyme to be used in this lab is called
catalase. This is an enzyme used to decompose hydrogen peroxide (H2O2), a toxic waste
product of metabolism.
catalase
2H2O2
2H2O + O2
In this experiment, the effect of various factors upon the rate of catalase activity will be
studied.
Materials:
- -100 mL graduated cylinder
- -10 mL graduated cylinder
- -3 test tubes
- -thermometer
- -universal indicator paper
- -500 mL beaker
-transfer pipettes
-hot plate
-crushed ice
-3% H2O2
-diluted liver puree
-1.0 M HCl and 1.0 M NaOH
Safety: Safety goggles are required for this lab.
Procedure:
Teacher Preparation:
Your teacher will prepare a stock solution for the class to share as follows: 150 g of beef liver
pureed with 1 L of distilled water. A personal stock solution for each group will be prepared
by diluting the beef liver puree (2.0 mL of the stock liver puree into 78 mL of distilled water).
PART A: Effect of Enzyme Concentration
1. Using a transfer pipette, add 8.0 mL of 3% H2O2 to the 100 mL graduated cylinder.
2. Using a transfer pipette, measure 1.0 mL of the diluted liver puree in the 10 mL
graduated cylinder. Add the liver puree to the H2O2 in the graduated cylinder.
3. Record the maximum height (in mL) of the foam produced. Be sure to subtract the
volume of solution at the bottom of the graduated cylinder.
4. Rinse the 100 mL graduated cylinder. Repeat steps 1, 2, and 3 nine times using 2 mL
of diluted liver puree, then 3 mL, 4 mL and up to 10 mL.
PART B: Effect of pH
1. Prepare the following mixtures in three separate test tubes:
Test Tube Mixture:
A
5 mL diluted liver puree and 2 drops of 1M HCl
B
5 mL diluted liver puree and 2 drops H2O
C
5 mL diluted liver puree and 2 drops of NaOH
2. Add 8 mL of H2O2 to the 100 mL graduated cylinder. Add the contents of test tube A
to the 100 mL graduated cylinder. Observe and record the maximum height of foam
produced.
3. Determine the pH of the mixture using universal indicator paper.
4. Rinse the 100 mL graduated cylinder. Repeat steps 2 and 3 with test tubes B and C.
PART C: Effect of Temperature
1. Add 8 mL of H2O2 to the 100 mL graduated cylinder. Add 5 mL of the liver puree to a
test tube. Immerse the test tube in an ice bath until the liver puree reaches a
temperature of approximately 10C.
2. Pour the contents of the test tube into the 100 mL graduated cylinder. Observe and
record the maximum height of foam produced.
3. Repeat the above procedure with the liver puree at room temperature (approximately
20C).
4. Use a water bath and hot plate to repeat the procedure with the liver puree at 40C,
60C and 80C.
PART D: Effect of Substrate Concentration
Using diluted liver puree, 3% H2O2 and 30% H2O2, design a procedure to measure the effect
of variations in substrate concentration on the rate of catalase activity. Include an
introduction, list of materials, and procedure.
Note: You will not be performing this part of the lab. Please include the design as an
"Appendix" in your lab report.