emphasis on quantitative skills did not reduce students’ mastery of
basic biological content. Thus, it is essential that science educators
make a concerted effort to provide students the opportunity to acquire
necessary skills in numeracy and data analysis.
Practical Considerations for
Investigation of the actions of enzymes is an essential part of an
introductory biology laboratory course. Unfortunately, many of
the available procedures possess certain drawbacks. One standard
method of investigating enzyme function in a laboratory classroom is through the use of an artificial substrate, which produces
a color change that can be measured by spectrophotometry. For
example, many teaching laboratories examine the activity of a
peroxidase using the artificial substrate guaiacol (Weinheimer &
White, 2003). While this method provides abundant quantitative
data, it requires that the instructor has access to expensive spectrophotometry equipment and supplies. Additionally, the artificial substrate may be costly, particularly for a larger course.
Specialized organic reagents can also necessitate special handling;
for example, the U.S. Environmental Protection Agency lists guaiacol
as a skin, eye, and respiratory irritant, and it is a volatile chemical that
produces an unpleasant odor in the laboratory. Special disposal procedures are also required for this chemical. At a time when budget shortfalls at the state and federal level have reduced educational funding, it
has become especially important for educators to find ways to reduce
costs in classroom laboratories without sacrificing the quality of students’ experiences.
On the other hand, procedures that do not require such equipment and reagents may provide qualitative, subjective, or only
semi-quantitative data (Clariana, 1991; Shmaefsky, 1993). Such
results can still enhance student understanding of the nature of
enzymes, an essential biological concept. However, they provide little or no potential for mathematical analysis. Instructors then lose a
valuable opportunity to help students improve mastery of quantitative skills, such as the preparation and interpretation of graphs, in a
Rationale for the New Procedure
Here, we present a novel procedure for investigating enzyme
activity in a classroom laboratory. This procedure takes advantage
of the fact that the yeast species Saccharomyces cerevisiae produces
a highly active catalase enzyme. Cleavage of hydrogen peroxide
(H2O2) by this enzyme is an exothermic reaction, and the
increase in temperature is readily measurable and is an indirect
indicator of enzyme activity. Equipment and supplies required
for the proposed experiment are minimal and nonhazardous.
The experiment renders reliable quantitative data. Moreover, the
initial procedure can be followed by a second class where it is
extended into a guided inquiry. In the experiential activity, the
instructor would provide only the baseline protocol and students
would then design their own investigation of factors influencing
Methods & Materials
Activated Yeast Solution: Fleischmann’s Active Dry Yeast obtained
from a convenience store was used for the experiment. A 10%
(w/v) suspension of yeast in 2% (w/v) sucrose solution was prepared by dissolving 0.5 g of sucrose in 25 mL of water and adding 2.5 g of yeast. This suspension was activated by incubating
for 30 minutes at room temperature prior to performing the procedures. This volume of yeast suspension is sufficient to perform
one set of the procedures described below. Fresh yeast suspension must be prepared and activated each time these procedures
Hydrogen Peroxide (H2O2): A freshly opened bottle of 3%
hydrogen peroxide solution from a medical store was used as a
substrate for the enzymatic reaction.
Thermometer: For measurement of temperature, a cylindrical
Fisher Scientific digital thermometer (catalog no. S01595) was used.
Similar results were obtained for baseline with a Carolina Biological
digital pocket thermometer (catalog no. 745360). For data collection, temperatures were measured in degrees Fahrenheit because
the temperature change is more pronounced compared to Celsius
and therefore easier for students to note.
pH: 1 M NaOH solution (Carolina Biological, catalog no. 889573)
was used to modify the pH for one of the experiments.
A summary of the laboratory procedures can be found in Table 1.
Baseline: 0.5 mL of 3% H2O2 and 0.5 mL of water was added
to a 50 mL graduated plastic tube (United Lab Plastics, catalog
Table 1. Summary of catalase enzyme activity laboratory procedures.
Substrate Enzyme Total Volume
(mL) 3% H2O2 (mL) H2O (mL) 10% Yeast (mL) H2O (mL)
Baseline 0.5 0.5 4 0 5
Temperature 0.5 0.5 4 0 5
2× Substrate 1 0 4 0 5
0.5× Enzyme 0.5 0.5 2 2 5
pH 0.5 0.5 4 0 5