Catalase Lab
Background:
The organic macromolecules required by living cells include proteins. Like other organic
macromolecules, proteins are made by linking monomers together via dehydration synthesis.
In the case of proteins, the monomers are amino acids, of which there are 20. Since
proteins vary in amino acid sequence and length, the possibilities for protein design are
endless.
While carbs and lipids are used by organisms for energy, proteins do the work of the cell:
building molecules, translating the DNA, etc. One class of proteins, enzymes, facilitate
virtually every chemical reaction that occurs in the cell. Enzymes are biological catalysts
that carry out the thousands of chemical reactions that occur in living cells. They are large
proteins made up of several hundred amino acids. Enzymes facilitate chemical reactions by
bringing the relevant molecules together so the reactions happen quickly. In an enzymecatalyzed reaction, the substance to be acted upon, or substrate, binds to the active site
of the enzyme. The enzyme then converts the substrate to the desired products. The
enzyme is not used up; it can be used again and again. One enzyme molecule can facilitate
thousands of reactions every minute.
Each enzyme is specific for a certain reaction; its active site has a specific shape and only
one or a few compounds present in the cell can interact with it. If the active site becomes
blocked or changes shape, the activity and efficiency of the enzyme is affected. If the
changes are large enough and the enzyme can no longer act at all it is said to be denatured.
Catalase (peroxidase) is one such enzyme found in all living things. It speeds up a reaction
that quickly breaks down toxic hydrogen peroxide (H 2O2) into H2O and O2 before it can do
any damage. In this lab you’ll run qualitative tests for catalase activity in different tissues
and under different conditions.
Procedure:
Part One: The Effect of Temperature on the Catalase Enzyme.
1.
Take some celery and grind it up using the mortar and pestle. Add some water to
the liquid and pour equal amounts into four test tubes. You want as much celery in
your liquid as possible. If needed, get some more celery and grind it up to add to the
liquid.
2. Make sure you wear your safety goggles! Get four test tubes and fill them each
with 10 drops of the liver solution. Place one tube in each of the water baths: 100ºC
(boiling), 70ºC, and 0ºC. The last tube, leave out at room temperature. These tubes
should stay in the water baths for 10 minutes.
3. Test each solution for catalase activity by adding 10 drops of hydrogen peroxide to
the test tubes. Swirl tubes to ensure evenly distributing all of the hydrogen
peroxide.
4. Record your observations in your data table.
Part Two: The Effect of pH on the Catalase Enzyme
1. Make more celery liquid by grinding it up using the mortar and pestle.
2. Pour liquid in even amounts into each of the 5 test tubes. If necessary, make more
celery mixture.
3. Before adding acids and bases to the test tubes, test the solutions to determine pH
using pH indicator paper. Record into your data table.
4. Put 10 drops of strong acid into tube #1.
5. Put 10 drops of weak acid into test tube #2 .
6. Put 10 drops water into test tube #3.
7. Put 10 drops of weak base into test tube #4.
8. Put 10 drops of strong base into test tube #5.
9. Add 10 drops of hydrogen peroxide to each test tube to test for catalase activity.
Swirl and observe.
10. Record observations into data table.
11. When you are finished. Rinse and dry your test tubes. Leave test tubes in the
racks upside down to dry before next class.
Name:_____________________________ Date:_______ Class:________
Pre-Lab questions:
1. For each part of the lab, what are the Independent and Dependent Variables?
2. What are the controls for each part of the lab?
3. What will each part of the lab be testing for?
4. Draw a picture of the reaction that the catalase enzyme helps.
Purpose:
Hypothesis:
Part 1:
Part 2:
Materials:
Data Tables:
Test
Tube #
Temperature Bubbles
(1, 2, or
3)
Test
Tube #
pH
Bubbles (1,
2, or 3)
Graphs: On another sheet of paper, create two graphs. In the first graph, graph the pH vs.
reaction rate (bubbles). In the second graph, graph the temperature vs. reaction rate
(bubbles).
Conclusion/Analysis:




Summarize the relationship between enzymes and substrates. Identify each in the lab.
What is the effect of catalase on hydrogen peroxide? Cite your data from the lab to support
your answer.
What variables affect enzyme reaction rate? In what way? Cite your data as evidence. Do
the results support your hypothesis? Explain.
Discuss potential and probable sources of error that affect the results. Consider both
errors of lab design and human error in completing the lab. Do you feel the results obtained
are conclusive? Why or why not?