An Exploration of Enzyme Activity
Introduction
The chemical hydrogen peroxide (H2O2) spontaneously decomposes into water and
oxygen gas:
2 H2O2 --2H2O + O2
The reaction happens very slowly, but over a number of years a bottle of peroxide
will convert almost entirely into water!
The enzyme CATALASE dramatically speeds the breakdown of hydrogen peroxide.
Catalase exists in the cells of many organisms, including humans, to reduce levels
of H2O2 that accumulate as a metabolic byproduct. The rate of the catalyzed
breakdown of hydrogen peroxide can be measured by the rate of O2 production.
In this investigation, the speed with which O2 bubbles cause a paper disk to rise
indicates the relative SPEED of the reaction. Your source of the enzyme will be
yeast (Saccharomyces cerevisiae) cells.
I. The tool for Measuring Reaction Rate
Before starting, you will learn how to measure the rate of the enzyme-catalyzed
reaction.
* Obtain a disk of filter paper.
* Drop disk into beaker with yeast/enzyme solution and let soak for a few
minutes
* Meanwhile, fill a small beaker or plastic cup with 2/3 hydrogen peroxide
* Use tweezers to move the paper disk from the yeast and into the hydrogen
peroxide. The disk will sink to the bottom- begin timing at the
moment the disk touches the bottom!
* The disk will float to the surface as it fills with oxygen bubbles produced
by the breakdown of H2O2.
* Stop timing when disk reaches top. Record in chart below
* Perform 2 more trials, and record.
II. The Investigation
What are some factors that could change the rate of the enzyme-catalyzed
breakdown of hydrogen peroxide? What might influence the effectiveness of catalase
at making the reaction occur? Brainstorm with your group and list your ideas
below.
Your group will choose one variable to investigate. Identify your control. You will
design an experiment to test if and how your variable influences the activity of the
enzyme. Be prepared to offer your experimental design to the class for constructive
criticism. Record your Title, hypothesis, materials, and data on your group’s Google
doc page.
III. Data Analysis and Conclusions
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Make any relevant mathematical calculations of your data on you Google doc.
You must graph your data on Excel.
Discuss and explain the meaning of your data with your group members.
Research your variable’s effect on enzyme activity by using your textbook
or the Internet.
IV. Your Google doc
Your Google doc must contain the following components:
* A Scientific Specific Title
* The names of everyone in your group
* One picture of your set-up
* Materials
* Procedure
* A paragraph explaining 1) what enzymes are, 2) what their role is, and 3)
explaining the chemical reaction
2 H2O2  2H2O + O2
* A GRAPH of your findings.
* One paragraph for EACH of the following in the conclusion:
- Explaining the effect of your variable on your experiment.
- How do your experimental findings compare with accepted
scientific knowledge of factors affecting enzyme activity?
Explain.
- What improvements would you make your experimental design
if you had more time and materials?