ENZYME CATALASE LAB
Catalase: Can the presence of enzymes in tissue be detected indirectly?
Objective: Demonstrate the activity of an enzyme in living tissues. Observe the effects of changes in temperature
on the activity of catalase.
Process Skills: Performing analyses for the presence of an enzyme in tissues. Analyzing relationships between
environmental conditions and enzyme activity.
Introduction: (READ EVERYTHING FIRST!!!!!!)
Even when functioning normally, your cells make poisonous chemicals. Enzymes break down these
poisonous chemicals into harmless substances. Enzymes are proteins that speed up the rate of reactions that would
otherwise happen more slowly. The enzyme is not altered by the reaction. The substrate is the molecule on which
the enzyme acts, and the products are the molecules produced by the reaction. You have thousands of different
enzymes in each of your cells. Each of these enzymes is responsible for one particular reaction that occurs in the
cell.
In this lab, you will study an enzyme that is found in the cells of many living tissues. The name of the
enzyme is catalase; it speeds up a reaction that breaks down hydrogen peroxide, a toxic chemical, into two
harmless substances, water and oxygen. The reaction is as follows: 2H2O2 2H2O+O2
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many
normal cellular reactions. If cells did not break down the hydrogen peroxide, they would be poisoned and die.
Under certain conditions, enzymes are denatured. An enzyme is denatured when it loses its proper shape
and cannot function. Some things that can denature an enzyme are
Materials:
high temperatures, extremes of pH, heavy metals and alcohol.
Hydrogen Peroxide
Graduated
In this lab, you will study the catalase found in potato cells.
Cylinder
You will use a potato from the grocery store. It might see strange to
Small Test Tubes 6
Test Tube Rack
use “dead” cells to study the function of enzymes by when a cell dies, (or 7)
the enzymes remain intact and active for several weeks, as long as the
Stirring Rod
Test Tube
tissue is kept refrigerated.
Holder
Thermometer
Potato
Pipet
Procedures:
PART A: NORMAL CATALASE ACTIVITY
0. PREP STEP: In the 50ml beaker, pour in Hydrogen Peroxide (H2O2) until the beak is about two
thirds full. Use this as your stock solution for the lab - DO NOT PLACE POTATO IN THIS BEAKER!!!
1. Caution: Hydrogen peroxide is a mild skin irritant. It will bleach fabric. Pipet 2mL of the hydrogen
peroxide solution into a clean test tube. Using forceps place a small piece of potato into the test tube. Push
the potato into the hydrogen peroxide with a stirring rod if it gets stuck. CAUTION: Use care when
handling glassware. (Note: Be sure to clean your stirring rod between steps.) Observe the bubbles.
Throughout this investigation, you will estimate the rate of the reaction (how rapidly the solution bubbles)
on a scale of 0-5. (0=No reaction,1=Slow, 5=Very Fast) Assume that the reaction in this step proceeded at a
rate of 3 and record the speed in Table 2 on the last page of this lab.
Control reaction rate: _____3_____
Observation:_____________________________________________________________
What gas is being released?________________________
2. A reaction that absorbs heat is endergonic and a reaction that gives off heat is exergonic. Feel the
temperature of the test tube with your hand.
Has the test tube gotten warmer or colder? ________________________
What type of reaction does this indicate? ________________________
Describe what is happening in your test tube. ________________________
3. Pour off the liquid into another test tube. Do not allow the potato to go into the other test tube. Set aside the
potato.
What is the liquid composed of (*hint* read the introduction)? ________________________
What do you think would happen if you added more potato to this liquid? ________________________
What do you think would happen if you added more peroxide to this liquid? ________________________
4. Split poured off liquid between two test tubes.
 In one test tube add another piece of potato.
What happened in this test tube? ____________________________________
Why do you think this happened? ___________________________________________
 In the other test tube add another 2mL of hydrogen peroxide
What happened in this test tube? ____________________________________
Why do you think this happened? ___________________________________________
5. Add another 2 mL of hydrogen peroxide to the potato remaining in the first test tube
Describe what you observe. ________________________
Are enzymes reusable? Why or why not? ________________________
PART B: EFFECT OF TEMPERATURE ON CATALASE ACTIVITY
6. put equal quantities of potato into three clean test tubes and 1 mL of hydrogen peroxide into three other test
tubes. Two test tubes will go in each water bath. Put one test tube containing potato and one test tube
containing hydrogen peroxide into each of the following baths: ice bath, room temperature, warm water (37
degrees Celsius). Allow this to sit for 3 minutes. Reset your timer and check your hot water bath in #8.
7. Remove the test tube from the hot water bath, allow it to cool, and then pour out the water. Add 2mL of
hydrogen peroxide. Record your reaction rate in the table and describe what happened below.
Hot water bath reaction rate:___________
Observation:_____________________________________________________________
8. After 3 minutes in the water bath (ice bath, room temperature, or warm water) pour each test tube of
hydrogen peroxide into its corresponding test tube of potato and observe the reaction.
Ice water bath reaction rate:___________
Observation:_____________________________________________________________
Room temp. water bath reaction rate:___________
Observation:________________________________________________________
Warm water bath reaction rate:___________
Observation:_____________________________________________________________
9. Obtain a piece of BOILED potato.
10. Place the BOILED Potato into a clean test tube.
Predict what boiling will do to an enzyme. ________________________
11. Add 2 ml to the tube containing the boiled potato
Boiled Potato reaction rate:___________
Observation:_____________________________________________________________
12. Record the reaction rates (0-5) in the Table. Graph the estimated reaction rate as a function of temperature
on the Graph paper on the next page. You should have five pints: 0 degrees Celsius (ice water), Room
Temperature (in degrees Celsius), 37 degree Celsius (human body temperature), and 100 degrees Celsius
(boiling).
Table 2 Relative Reaction Rates of Live Catalase as a Function of
Temperature
Temperature
Rate of Enzyme Activity
___________3____________
Control reaction rate:
(0 oCelsius) Ice water bath reaction
rate:
Room temp. water bath reaction rate:
(37 oCelsius) Warm water bath
reaction rate:
(100 oCelsius )Boiled Potato reaction
rate:
________________________
________________________
________________________
________________________
What is the “optimum” temperature for catalase? ________________________
Explain why the reaction proceeded as it did at 0 degrees Celsius and 100 degrees Celsius.
__________________________________________________________________________________________
__________________________________________________________________________________________
3
2
1
0
Reaction Rate
4
5
On Graph 1, using dot and line style graphing (connect the dots) plot the data from Table 2.
Graph 1 Relative Reaction Rates of Potato Catalase as a Function of Temperature
Control
O
Room
37
100
Degrees Temp Degrees Degrees
Temperature (Degrees Celsius)