Name: _____________________________________________________ Date: ___________ Block: _______
Science Research Investigation:
Do various organisms differ in their catalase activity?
Introduction to Enzymes:
What would happen to your cells if they made a poisonous chemical? Do you think that your cells would
die? Oddly enough, your cells are always making poisonous chemicals, but they do not die because your cells
use enzymes to break down these poisonous chemicals into harmless substances. Enzymes are proteins that
speed up the rate of chemical reactions that would otherwise happen more slowly. The enzymes are not
altered by the reaction so they are re-usable. You have hundreds 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. Catalase speeds up a reaction, which breaks down hydrogen peroxide (a toxic chemical)
into water and oxygen. This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a
byproduct of many normal cellular reactions. If the cell does not break down the hydrogen peroxide, they would
be poisoned and die. The reaction is written as follows: 2H2O2
2H2O + O2
In this lab, you will study the catalase found in liver, potato, ad yeast cells. You will be using beef liver
that your teacher purchased in the supermarket. It might seem strange to use dead tissues to study the
function of enzymes. However, is possible because when a cell dies, the enzymes remain intact and active for
several weeks, as long as the tissue is kept refrigerated.
Adapted from: Towle, Albert. "Catalase Laboratory." Modern Biology. Austin: Holt, Rinehart and Winston, 1989. Print.
Prelab Demonstration: What is the purpose of this reaction?
A. Measure approximately 5 mL of the hydrogen peroxide into a clean test tube.

Is the hydrogen peroxide bubbling?
B. Measure 5 mL of liver solution into the other clean test tube. Pour the test tube with the hydrogen peroxide
into the test tube holding the liver solution.

Notice that this reaction produces bubbles. What gas is being released?
C. Recall that a reaction that absorbs heat is endothermic; a reaction that gives off heat is exothermic. Now,
feel the temperature of the test tubes with your hand.

Has the test tube gotten warmer or cooler? Is the reaction endothermic or exothermic?

What do you think is happening in your test tube to cause this reaction to happen?

What is this liquid composed of? What do you think would happen if you added more liver solution to this
liquid?
D. Add another 5 mL of liver into the test tube holding the liver extract.

Do you observe any reaction? Why or why not?
E. Add another 5 mL of hydrogen peroxide into the test tube holding the liver extract.

Do you observe any reaction? Based off your observations, are enzymes reusable? Explain.
Guided Inquiry: Does catalases rate of reaction differ in various organisms?
Materials:
- stop watch
- tubing
- glass dropper tube
- stopper
- (2) 10 mL graduated cylinder
- (1) 100 mL graduated cylinder
- (1) 250 mL flask
- (1) shallow pan for water bath
Enzyme
Substrate
- (3) 250 mL beakers
- (2) funnels
- Premade solutions of: H2O2, liver,
potato, and yeast solution
Product(s)
Potato Solution
Liver Solution
Yeast solution
Null Hypothesis: _________________________________________________________________________
________________________________________________________________________________________
Alternate Hypothesis 1: (If/Then/Because): ____________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
Alternate Hypothesis 2: (If/Then/Because): ____________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Fill a container 3/4th full of water and submerge a 100 mL graduated cylinder in the water.
Measure 10 mL of hydrogen peroxide (diluted with water by 50 percent) in a graduated cylinder.
In a second graduated cylinder measure 10 mL of the potato solution.
Place the rubber tubing into the submerged graduated cylinder (keeping the mouth of the graduated
cylinder under the water) invert the cylinder. Make sure the cylinder is full of water with no air pockets.
Pour the potato solution into the flask and then add the hydrogen peroxide. Quickly place the stopper on
the flask and gentle swirl.
Begin the timer when the first bubble appears in the cylinder and stop the timer then the bubbles cease.
Collect the amount of water displacement (mL) over time (sec) in the chart below.
Repeat steps 1 through 7 using the liver solution.
Repeat the experiment two times for each solution and share that data with the class.
Figure 1: Materials
Figure 2: Set up of apparatus
Table1: The type of tissues’ effect on the catalase’s reaction rate (mL/sec)
Amount of O2 Produced (mL/sec)
Trial
Catalase found in Potato
Catalase found in Liver
Catalase found in Yeast
1
2
Your
Average:
Class
Average:
Graph: Include a title; label the x and y axes, and make a key that represents the class and your calculated
averages using a bar graph.
Title: _________________________________________________________________________
Possible Research Questions: Concept Map
What variables do you think might be
important in the function of this enzyme?