Names: _______________________________________________ LabQuest
6A
Biology with Vernier
6A - 1
Enzyme Action:
Testing Catalase Activity
50 Points
Many organisms can decompose hydrogen peroxide (H2O2) enzymatically. Enzymes are globular
proteins, responsible for most of the chemical activities of living organisms. They act as
catalysts, substances that speed up chemical reactions without being destroyed or altered during
the process. Enzymes are extremely efficient and may be used over and over again. One enzyme
may catalyze thousands of reactions every second. Both the temperature and the pH at which
enzymes function are extremely important. Most organisms have a preferred temperature range
in which they survive, and their enzymes most likely function best within that temperature range.
If the environment of the enzyme is too acidic, or too basic, the enzyme may irreversibly
denature, or unravel, until it no longer has the shape necessary for proper functioning.
H2O2 is toxic to most living organisms. Many organisms are capable of enzymatically destroying
the H2O2 before it can do much damage. H2O2 can be converted to oxygen and water, as follows:
2 H2O2
2 H2O + O2
Although this reaction occurs spontaneously, enzymes increase the rate considerably. At least
two different enzymes are known to catalyze this reaction: catalase, found in animals and
protists, and peroxidase, found in plants. A great deal can be learned about enzymes by studying
the rates of enzyme-catalyzed reactions. The rate of a chemical reaction may be studied in a
number of ways including:
• measuring the rate of appearance of a product (in this case, O2, which is given off as a gas)
• measuring the rate of disappearance of substrate (in this case, H2O2)
• measuring the pressure of the product as it appears (in this case, O2).
In this experiment, you will measure the rate of enzyme activity under various conditions, such
as different enzyme concentrations, pH values, and temperatures. It is possible to measure