Grade Level/Subject
9 / Biology
Unit
Biochemistry
Enduring
Understanding
Most cell functions involve chemical reactions
and many of these chemical reactions are
catalyzed by enzymes. Enzyme function is
related to enzyme structure.
BIO.2
The student will investigate and
understand the chemical and
biochemical principles essential for life.
Key concepts include
c) the nature of enzymes.
BIO.1
The student will demonstrate an
understanding of scientific reasoning,
logic, and the nature of science by
planning and conducting investigations.
Influencing the Rate of Enzyme Activity
SOL Objectives
Title
Lesson Objective
Inquiry Level
Materials Required
Students will be able to conduct an experiment
to determine the rate of enzyme activity and
the effect of one or more variables (including
temperature, pH, and concentration) on the rate
of enzyme activity.
2 (Question and Methods Given; Solution Open)
Test tubes, hydrogen peroxide, cheesecloth or
filter paper, single-hole punch, rulers,
Sharpies/marking pens, timers/stopwatches,
potatoes, blender, forceps, stirring rod, funnel,
distilled water, HCl or a similar acid, NaOH or a
similar base, hot plate, ice.
1
Influencing the Rate of Enzyme Activity
Enzymes are proteins that act as biological catalysts. They allow a chemical reaction to occur
more quickly because they lower the amount of energy required to start the reaction (activation
energy).
Hydrogen peroxide, H2O2, is a byproduct of normal metabolic activity in cells. However, if it
accumulates, hydrogen peroxide damages the cell and can lead to cell death. Hydrogen peroxide
slowly breaks down into harmless water and oxygen gas according to the following equation:
Without an enzyme, this reaction would proceed rather slowly. However, in a cellular
organelle called the peroxisome, an enzyme called catalase speeds up this reaction and prevents
the accumulation of hydrogen peroxide.
In this investigation, you will conduct experiments to determine the rate at which catalase
converts hydrogen peroxide into water and oxygen gas. You will use catalase from potatoes.
The speed of the reaction will be determined by measuring the rate at which oxygen gas is
produced. A filter-paper disk coated with potato extract containing the enzyme (catalase) is
placed into a test tube containing the substrate (hydrogen peroxide solution). As catalase
decomposes hydrogen peroxide into water and oxygen gas, bubbles of oxygen collect on the
disk. When the density of the combined paper/enzyme/O2 is less than the solution the disc will
rise to the surface. The time it takes for the filter-paper disk to rise to the top of the solution can
be used to measure the rate of enzyme activity.
Materials:
forceps
test tubes & test tube rack
filter paper
potatoes (fresh)
hole punch (to make paper discs)
blender
hydrogen peroxide
stirring rod
ruler
Sharpie
timer/stopwatch
2
Method for data collection:
Part I. Baseline Data
1. Peel potatoes and blend them in a regular kitchen blender; filter to remove particles and
obtain a liquid extract. Keep extract supply cold until ready to use. (Note: Your teacher
may have already completed this step for you).
2. Take ~ 30 mL of extract to your table in clean 50 mL beaker
3. Select 5 test tubes and label them A, B, C, D, and E.
4. Measure up 5 cm from the bottom of each test tube and mark this height on the test tube.
5. Fill each test tube to the 5 cm mark with 3% hydrogen peroxide.
6. Cut out 5 uniform discs of filter paper using a paper hole-punch.
7. Soak each filter paper disc in potato liquid extract then dry the discs for 5 seconds on paper
towel to remove excess moisture.
8. Use clean forceps or a glass stirring rod to place each disc at the bottom of its own test tube.
9. Measure the time it takes for disc to reach surface of solution in test tube. Record this in
your data table.
10. Calculate the rate of enzyme activity using the equation: Distance = Rate x Time; record in
your data table.
Part II. Designing Your Own Experiment
11. Using these same basic steps, develop a modified procedure to test the effect of one of the
following variables on the rate of enzyme activity: temperature, pH, enzyme concentration,
or substrate concentration. Record all information, including your hypothesis and variables,
in the appropriate place on your data and analysis sheet.
12. Once your procedure has been approved by your teacher, carry out your procedure and
record your data.
13. Clean up your lab area as instructed by your teacher.
14. Graph your data; be sure to give your graph a title, label both axes (include units), and use
the appropriate type of graph.
15. Write a conclusion in which you summarize what happened and explain what your data
mean.
3
Influencing the Rate of Enzyme Activity
Data Table 1: Baseline data
Test Tube
Time for disk to rise
(s)
Distance (cm)
A
5
B
5
C
5
D
5
E
5
AVERAGE
5
Rate of Activity
(cm/s)
Part II. Designing Your Own Experiment
Identify the following:
Independent Variable: __________________________________________________________
Dependent Variable: ___________________________________________________________
Control: _____________________________________________________________________
Constants: ___________________________________________________________________
Hypothesis: ________________________________________________________________________
___________________________________________________________________________________
Procedures: In the space on the following page, write out detailed procedures. Be very specific so that anyone
could read your procedures and replicate your experiment exactly. Follow your teacher’s directions as to whether
these procedures should be in paragraph form or in a numbered or bulleted list.
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Data Table 2: Experimental data
Test Tube
Time for disk to rise
(s)
Distance (cm)
A
5
B
5
C
5
D
5
E
5
AVERAGE
5
5
Rate of Activity
(cm/s)
Graph – On the graph below, show your average data for both the baseline data and your own experiment.
Give the graph a title, label both axes (include units), and make sure you use the appropriate type of graph.
Title: _______________________________________________________________
Conclusion:
Summarize your results (both the baseline data and the data you collected from your own
experiment).
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6
Explain what your results mean in terms of enzyme function/activity and the impact of the variable
you tested on enzyme activity. You may ultimately decide to consult your textbook or online
resources to help you interpret your results.
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What are the possible sources of error in this experiment?
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How could you improve this experiment?
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Find a group in class who tested a different independent variable; talk with them about what they
tested, how they did it, and what they found out. In the space below, identify what variable that
group tested and how that variable influences the rate of enzyme activity.
Another group in class tested the effect of ________________________________________________
on enzyme activity. Based upon the results of their experiment, what is the effect of this variable on
enzyme activity?
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