Catalase Lab
You are making poisonous chemicals in your body right now! Where do they come from? They are a product of cellular metabolism. Why
don’t you or your cells die? These poisons are very quickly changed into harmless substances by special proteins called enzymes. Enzymes
work by speeding up the chemical processes that would otherwise take a long time. There are thousands of different enzymes in your body,
and each of them specializes in a particular biochemical reaction…including the reactions that create toxins in the first place.
In this lab, you will study an enzyme that is found in many living tissues(plant and animal). The name of the enzyme is catalase, and it is
responsible for breaking down hydrogen peroxide(toxin) into water and oxygen(two harmless substances). Here is the chemical reaction:
2 H2O2

(hydrogen peroxide)
2 H2O + O2
(water)
(oxygen)
You will notice that the formula for the reaction is balanced, meaning that there are the same number of each element on either side of the
reaction. The substance that is acted on by the enzyme is called the substrate. Through its chemical reaction, the enzyme turns the substrate
into products. For our lab, we will be using chicken or beef liver as the source of our catalase. A 3% hydrogen peroxide solution will be our
source of the substrate. How are dead liver cells able to make a chemical reaction occur? Even though the cells are dead, many enzymes
remain intact for weeks under the proper conditions(refrigeration). Since the shape of the enzyme determines its function, the enzyme
continues to work as long as it holds its shape. When an enzyme denatures(loses its shape), it is no longer able to make the reaction take
place. There are a number of factors that can cause a protein to denature: high temperatures, extremes of ph, heavy metals, and alcohol.
Baseline Catalase Activity – The rest of this lab will be based on the reactions you observe in this first experiment. On a scale of 0 to
5, we will assign the reactions in this section a “4”. In other words: 0 = no reaction 1= very slow 2= slow 3= medium
very fast reaction. To determine the reaction rates of other experiments, you must reference this experiment.
4 = fast
5=
Fill each of three test tubes with 2 mL of hydrogen peroxide. Cut two plain M&M sized pieces of liver. Using a stirring rod, insert one of the
pieces of liver into the hydrogen peroxide of one of the test tubes. Write your qualitative and quantitative observations in the space below.
Now, pour out the fluid and obtain the “used” piece of liver. For the second part of this experiment you will place the “used” piece of liver
into one of the clean test tubes. As a control, place the remaining fresh piece of liver into the last clean test tube. Compare the reaction of the
“used” liver to that of the “fresh” piece of liver. Include all observations in the space below. If you are unsure of your results repeat the
experiment (pouring the peroxide over the liver gives a different perspective). Regardless, you must KNOW what a “4” looks like to proceed.
Baseline Observations –
Alcohol and Catalase – What is the effect of ethyl alcohol(ethanol) on the catalase enzyme? Starting with four test tubes, put M&M
sized pieces of liver at the bottom of two of the test tubes and fill the remaining two test tubes with 2mL of hydrogen peroxide. Pour ethanol
over the liver in one of the test tubes. Allow the liver to soak for at least five minutes. Pour out the alcohol. With both pieces of liver ready,
pour the hydrogen peroxide over both pieces at the same time. Write your observations and conclusions below.
Observations-
Occurrence of Catalase – Catalase is present in many kinds of tissues. In this part of the lab, you will test for the presence of catalase
in a variety of tissues. You should have a solid grasp of what a “4” looks like by now(both liver into H2O2 and H2O2 poured over
liver)…remember that you are rating each reaction as it relates to the reaction rate of liver and hydrogen peroxide. Try to test all of the
tissues at the same time. If there aren’t enough test tubes to do this, it is acceptable to perform them separately. Since you are pouring the
H2O2 over the liver, make sure to use the correct “4” for comparison. Enter your findings and observations in the space below.
Observations –
Tissue
Rate of
sample
activity (0-5)
Temperature and Catalase – Different temperatures have varying effects on catalase activity. Ever cook an egg? What happens to the
appearance of the egg as it cooks? The changes in color and texture are caused by the change in shape(denaturing) of the proteins in the egg.
First we are going to cook some liver…boil it to be exact. We will also test catalase activity in a variety of temperature environments.
Boil – Put an M&M sized piece of liver in the bottom of a test tube and pour in just enough water to cover it. Place this test tube in the
boiling water bath for five minutes. Use test tube clamps to remove the test tube and pour out the water. Pour 2 mL of hydrogen peroxide
over the boiled liver. Enter your findings and observations in the space below.
Temperatures – Place liver pieces in the bottom of three test tubes with just enough water to cover. Fill three more tubes with 2 mL of H 2O2.
Place one liver tube and one hydrogen peroxide tube into each of the three water baths: ice bath(0°), room temp. bath(~23°), warm water
bath(37°). Let them sit for five minutes in the baths. Now, pour each of the test tubes of hydrogen peroxide into their corresponding liver test
tubes. Enter your findings and observations in the space below. Also make a graph of your data in the provided outline.
Observations-
Temperature
C°
rate of
activity (0-5)
Catalase and pH – The acidity or alkalinity of an environment is also important to the function of an enzyme. In this portion of the lab,
you will set up three different pH environments in which to test catalase. pH is how we measure the concentration of hydrogen ions in a
solution. Lower pH numbers are acidic and indicate higher concentrations of hydrogen ions, while higher numbers are alkaline and indicate
lower concentrations of hydrogen ions. You will use pH paper to test the hydrogen concentrations of your solutions. To test your solution,
dip a stirring rod into your test tube and then touch it to the pH paper. Make sure to thoroughly rinse the stirring rod between tests.
Starting with three test tubes, fill each with 2mL of hydrogen peroxide. Using hydrochloric acid and sodium hydroxide(alkaline), adjust the
three test tubes so that their pH levels are 3, 7, and 10 respectively. This is a very delicate process. It is better to add very small amounts(less
than a drop) so that you don’t overshoot your target. Your goal is to add as little to your test tubes as possible while adjusting pH to the
correct levels. Once you have established your tubes, insert an M&M sized piece of liver into each of them and record your results below.
This time create your own graph in the space provided. The graph should show catalase activity as it relates to pH. Please use a ruler!
Observations –
pH
rate of
activity (0-5)
Q1. Write out the balanced equation for catalase and show how it is balanced.
Q2. In your experiments, what was the enzyme? The substrate? The products?
Q3. Is the catalase in liver reuseable? Explain your answer with details from your experiments.
Q4. During the reaction, what gas do the bubbles consist of? After the reaction, what is the fluid that is left in the test tube?
Q5. If you could see the SHAPE of catalase enzymes before and after being soaked in alcohol, what do you think you would see?
Q6. Why do you think different animal and plant tissues would have varying amounts of catalase enzyme within them?
Q7. Explain why the liver that was boiled did not have a reaction?
Q8. Explain why you think the temperature/pH environment of an enzyme is important? Hint: What is the temperature/pH of a cow?
Q9. Did you feel a temperature change during the catalase reaction? Describe it. How do you think this affects an entire organism like a cow?
Q10. If you wanted to stop the catalase reaction without destroying it, what environment would you put catalase in?
Lab supplies for setup:
-liver, chicken, carrots, potato, apple
-hydrogen peroxide
-ethanol
-pipettes
-test tube clamps
-forceps
-test tubes
-test tube racks
-dissecting trays
-razors
-stirring rods
-hot plates
-1000mL beakers
-ice bath
-pH paper
-HCl and NaOH
-