Catalase Lab
* You will be required to wear goggles for this lab
* Remember that hot glass looks the same as cool glass! Please use the clamps for removing your test tubes
*You are responsible for cleaning up your lab area! Please place your used chicken liver samples (in the test
tube) at the end of the lab table in the designated test tube rack.
Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly. The
enzyme is not altered by the reaction. 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; it speeds
up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and
oxygen.
The reaction is: 2 H2O2 ----> 2 H2O + O2
This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of
many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned
and die. In this lab, you will study the catalase found in liver cells. You will be using chicken liver. It might
seem strange to use dead cells to study the function of enzymes. This is possible because when a cell dies, the
enzymes remain intact and active for several weeks, as long as the tissue is kept refrigerated.
Materials:
-Test tubes and rack
-Graduated cylinder
-Hydrogen Peroxide (3%)
-Pre-cut chicken liver samples (located at end of stations) YOU WILL NOT BE CUTTING
ANYTHING FOR THIS LAB!
-Clamps for test tubes (located need hot plates)
Directions:
1) Pour 2 mL of Hydrogen Peroxide into a clean test tube
2) Place a pre-cut piece of chicken liver into this test tube
3) Answer the following questions:
a) What gas is being released? (Look at the equation)
b) You will be recording the reaction rate (how many bubbles you see) during this lab. As a
reference, this rate is a 4 (on a scale of 1-5)
4) A reaction that absorbs heat is endothermic; a reaction that gives off heat is exothermic. Now, feel the
temperature of the test tube with your hand.
a) Has it gotten warmer or colder?
b) Is the reaction endothermic or exothermic?
5) Pour off the liquid into a second test tube when the reaction is complete. What is this liquid mostly
composed of?
6) Add a new piece of chicken liver to the liquid you just poured into a new test tube.
a) What is this reaction rate? (1-5)
7) Using the chicken liver used for the first part, add 2 mL of new Hydrogen Peroxide.
a) What is this reaction rate? (1-5)
b) Is catalase reusable? Why or why not?
8) In a new test tube, place a new piece of chicken liver and add about 3 mL of tap water
9) Place this test tube in a boiling water bath for about 5 minutes.
10) Using the clamps, remove your test tube from the hot water bath and place in the test tube rack.
Allow to cool for at least 2 minutes. Turn your hot plat down so that it is no longer boiling (about a 2 or 3).
11) Pour out the water and add in 2 mL of Hydrogen Peroxide.
a) Record this reaction rate. (1-5)
12) Place a piece of chicken liver into each of two new test tubes.
Place 2 mL of Hydrogen Peroxide into each of two new test tubes (Do not combine)
Place 1 of the Hydrogen Peroxides and one of the chicken livers into the refrigerator.
Place the other Hydrogen Peroxide and the other chicken liver into the warm water bath (Not boiling)
Let this sit for 2-3 minutes.
13) Pour the warm Hydrogen Peroxide into the warmed chicken liver.
a) Record this reaction rate: (1-5)
14) Pour the cooled Hydrogen Peroxide into the cooled chicken liver.
a) Record this reaction rate: (1-5)
Extra Credit pH: If you finish the lab with at least 10 minutes left over, please complete the following section
for extra credit added to your lab and participation grade. These solutions are located on the lab cart.
1) Add 2 mL of Hydrogen Peroxide to new test tubes.
2) In test tube 1, add 4 drops of vinegar (acidic). Record the pH using test strips: ___
3) In test tube 2, add 4 drops of the baking soda solution (basic). Record the pH: ___
4) Add chicken liver to each of the test tubes. (Try to do this at the same time to compare)
5) Reaction rate for acidic solution (1-5):
6) Reaction rate for basic solution (1-5):
Lab Questions: Please answer these questions on your own paper.
1) Describe the relationship between catalase and hydrogen peroxide. Indicate which is the enzyme, which is
the substrate and what occurs during the reaction. It may be helpful to write the equation.
2) Is catalase reusable? Use your data to support your answer.
3) How does temperature affect the reaction rate of catalase? Propose a way to refine your experiment to find
the exact, or OPTIMAL temperature of catalase.
4) Extra Credit only: How does the pH affect the reaction rate of catalase? Propose a way to refine your
experiment to find the optimum pH of catalase.
5. In 2-3 sentences, summarize the data and information displayed in this graph.