Investigating Factors That Affect Rate of
Enzyme Action
Subject: Living Environment/Biology
Grade Level: 9th and 10th
Unit: Biologically Important Molecules
Duration: 8 Fifty minute class periods
a) Part 1

3 class periods to explore the properties of enzymes, models of enzyme
action and the factors that affect rate of enzyme activity
b) Part 2

2 class periods to formulate a testable hypothesis and design an
experimental procedure

2 class periods to conduct the inquiry based lab activity

1 class period to present data and results to the class
Purpose: Students investigate factors that affect the rate of enzyme action.
Catalase will be used as the model enzyme to investigate the factors that affect
rate of enzyme action.
Objectives: Students will be able to (SWBAT):
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develop an understanding of the structure and function of enzymes
understand how the shape of an enzyme is related to its function
describe the characteristics of enzymes
explain the lock and key and induced fit models of substrate binding
use appropriate scientific terms to describe the functions of an enzyme,
such as substrate, product, activation energy, active site and enzymesubstrate complex
determine the factors that affect the rate of enzyme activity
explain how each factor (ie. pH, temperature, concentration of
enzyme/substrate) alters the rate of enzyme activity
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formulate a hypothesis about the environmental factors that will alter the
rate of enzyme activity
design an experiment to test their hypothesis
collect and analyze data as well as draw valid conclusions from data
present their experimental findings to the class by creating a poster
Prior Knowledge: Students will have an understanding of the four classes of
biologically important compounds (ie. carbohydrates, fats, proteins and nucleic
acids). In particular, students will have an understanding of the different levels of
protein structure as well as the various functions of proteins
Essential Questions:
1.
2.
3.
4.
5.
What is an enzyme? How do enzymes affect a chemical reaction?
What are the general characteristics/properties of enzymes?
Describe the two models used to explain the catalytic activity of enzymes
What are the factors that affect the rate of enzyme action?
Explain how temperature affects enzyme activity? What is meant by
optimum temperature?
6. Explain how pH affects enzyme activity? What is meant by optimum pH?
7. Explain how changes in enzyme or substrate concentration affect an
enzyme's behavior?
Preparation and Procedure:
Part 1: WebQuests
1.
Students will complete a K-W-L chart on enzymes.
2.
Students will work in groups of two or three to complete WebQuests that
explore the
a) structure and function enzymes.
b) models used to explain the catalytic activity of enzymes (ie. Lock and
Key and Induded Fit models).
c) characteristics of enzymes.
d) factors that affect the rate of enzyme activity.
3.
Use the Essentials Questions to guide students during the WebQuest.
4.
Teacher Tip:
a) Print out hard copies of each of the websites used for the
WebQuests in the event that students are unable to connect to the
Internet.
For a class size of twenty-four students working in groups of 3,
print out eight copies of each website to be used in during the
WebQuests.
b) For each of the four topics being explored limit the number of
websites that address each topic to only two.
5. Students will work in groups of two or three to formulate potential
experimental questions to test various factors that affect the rate of
enzyme activity. Experimental questions will be posted on either
newsprint or an overhead transparency.
Website Resources:
1. Animations/Tutorials
a) The Biology Place: LabBench Activities – Lab 1: Enzyme Catalysis
b) Interactive Concepts in Biochemistry – Interactive Animations: Enzyme
Specificity
Part 2: Inquiry Based Lab Activity (5 class periods)
Background Information:
Catalase will be used as the model enzyme to investigate how temperature,
enzyme or substrate concentration, salt concentration and/or changes in pH
affect the rate of enzyme action. Hydrogen peroxide is a toxic byproduct of
metabolism. Catalase speeds up the breakdown of hydrogen peroxide into water
and oxygen gas. This enzyme can be found in plant and animal cells as well as
aerobic bacteria. The generation of oxygen gas bubbles can be used to
quantitatively assess the affect of various environmental conditions on the rate of
catalase activity.
1. Students will work in groups of two or three to:
1.
(a) formulate a hypothesis to answer one of the experimental questions
posed by the class at the end of Part 1.

Once the instructor has approved their hypothesis, the students
in the group will begin to discuss an experimental procedure to test
their hypothesis.
(1) Homework: Students will complete their procedures at home.
Students may conduct research using the Internet in order to design their
procedure.
(b) Students will review each other’s procedures in class before deciding
on a final procedure to submit to the instructor for approval.
2.
Once the instructor has approved the procedure students will carry out
their experiment during their assigned laboratory period.

(a) Teacher Tips for Laboratory Preparation:
When reviewing student experimental procedures be sure that:
(1) potato samples being tested are the same size
(a) Students can use cork borers to obtain potato samples
and trim them using a scalpel or razor blade to the desired length.
(2) potato extract tends to give more consistent and reliable
results.
(a) Use 4-ply cheesecloth obtained from a science supply
company (E&K Scientific) to filter the extract.
(b) Be sure to keep the potato extract on ice at all times.
(3) students have included a control in their experimental design
(4) students are testing only one variable
 Some factors that students may investigate are:
(1) Changes in temperature
(2) Effect of different salt concentrations (ie. 1%, 2%, 3%, etc)
(3) Effect of enzyme concentration
(a) The initial extract can be considered 100% catalase.
Students can perform a serial dilution by mixing the extract with deionized
water to obtain concentrations of 80%, 60%, 40%, and 20% catalase.
(b) Be sure to keep the peroxide solutions in a brown
solution bottle.
(4) Effect of substrate concentration
Students can perform a serial dilution using 40 volume (12%)
cosmetics grade hydrogen peroxide to obtain lower concentrations of
hydrogen peroxide.
Cosmetics grade hydrogen peroxide can be purchased from a
beauty supply store. Be sure to use deionized water when performing
these dilutions.
(5) Effect of pH
Students should use solutions that have pH values of 1, 3, 5, 7,
10, and 12. Solutions with these pH values can be prepared using 1M
HCl and 1M NaOH.
Be sure to use pH test strips to verify the pH of each test solution.

Safety: Students will be expected to include a list of safety
precautions as part of their experimental design.
(a) Teacher Tip: Be sure students include safety
procedures/precautions for the following:
(i) handling of hot objects and hot plates,
(ii) use of thermometers
(iii) checking glassware for chips, cracks and stars
(iv) cleanup and disposal of broken glassware
(v) cleanup and disposal of spilled liquids
(vi) disposal of unused liquids
(vii) handling of sharp objects like scalpels or razor
blades
(viii) use of personal protective equipment:
goggles, apron or lab coat, latex or nitrile gloves
(some students may have an allergic reaction to
latex so it is advisable to have a non-allergenic substitute)
3. The students will be given time during the class period following
the laboratory activity to summarize their data and present their
results to the class using newsprint or overhead transparencies.
Students will also be expected to complete the “L” section on the KW-L worksheet.
4.
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Teacher Preparation for Part 2:
a) Possible experimental procedures for this laboratory activity
can be found by reviewing the following:
Topic 5: Enzymes - Catalase
Smith College Biology Department
The Properties of Enzymes – A Study of Catalase
Cornell Institute for Biology Teachers:
Science Assessment Prompt - Course: Biology – Enzyme
Catalyzed Reactions
Materials:
Part 1: WebQuests
 K-W-L worksheet for each student on enzymes and characteristics of
enzymes
 WebQuest Worksheets for enzyme structure and function, models
used to explain the catalytic activity of enzymes, characteristics of
enzymes and factors that affect rate of enzyme activity

Print copies of websites used for the WebQuests

Laptop computers with Internet access

LCD projector
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Overhead projector
 Newsprint or an overhead projector and transparencies to record
student responses to the K-W-L worksheet.
Part 2 – Inquiry Based Lab
test tubes
test tube rack
test tube holder
Sharpie marker
10 mL graduated cylinders
Potato pieces or potato extract
Mortar and pestle
Cosmetics Grade Hydrogen peroxide - 40
volume (12% hydrogen peroxide)
Sodium chloride
wash bottle with deionized water
30 centimeter ruler
hot plates
blender
4-ply cheesecloth
cork borer with 4 or 6-mm inside diameter
gloves
goggles
Stop watch
apron
disposable transfer pipettes
1M hydrochloric acid
1M sodium hydroxide
vinegar
400-mL beakers
Ice
Alcohol thermometers
Newsprint for presentation of results
graph paper
ice bucket
weighing boats
Suggestions for Assessment:
· Evaluate the completion of the WebQuest worksheets.
· Evaluate the “L” column for the K-W-L worksheet.
· Evaluate the group presentation of data and results.
National Science Education Standards:
1.
National Science Educations Standards – Grades 9 to 12
a)
Science as Inquiry:

Abilities necessary to do scientific inquiry

Understandings about scientific inquiry
b) Life Science:
 The Cell
c) K-12 Unifying Concepts and Processes:

Evidence, models, and explanation
 Change, constancy, and measurement
 Evolution
and Equilibrium
New York State Standards:
1. Standard 1: Students will use mathematical analysis, scientific inquiry, and
engineering design, as appropriate, to pose questions, seek answers, and
develop solutions.
a) Key Idea 1 - The central purpose of scientific inquiry is to develop
explanations of natural phenomena in a continuing and creative process.

Performance indicators 1.1, 1.2, 1.3
b) Key Idea 2 - Beyond the use of reasoning and consensus, scientific inquiry
involves the testing of proposed explanations involving the use of conventional
techniques and procedures and usually requiring considerable ingenuity.

Performance indicators 2.1, 2.2, 2.3, 2.4
c) Key Idea 3 - The observations made while testing proposed explanations,
when analyzed using conventional and invented methods, provide new insights
into natural phenomena.

Performance indicators 3.1, 3.2, 3.3, 3.4, 3.5
2. Standard 4: Students will understand and apply scientific concepts,
principles, and theories pertaining to the physical setting and living environment
and recognize the historical development of ideas in science.
a) Key Idea 1 - Living things are both similar to and different from each other
and from nonliving things.
 Performance Indicator 1.2 - Describe and explain the structures and
functions of the human body at different organizational levels (e.g., systems,
tissues, cells, organelles).
1)
Major Understandings 1.2h
b) Key Idea 5 - Organisms maintain a dynamic equilibrium that sustains
life.
 Performance indicator 5.1 - Explain the basic biochemical processes in living
organisms and their importance in maintaining dynamic equilibrium.
1) Major Understandings 5.1f and 5.1g