BIO 183 / BIO183 Lab 2 Unit 2
Exploring Properties of Enzymes
LEARNING OBJECTIVES
1. Define the properties and role of enzymes in biological systems.
2. Evaluate data and construct an argument for why the activity of the enzyme changes under multiple experimental
conditions.
3. Design an experiment to determine the effects of various experimental conditions on the enzyme catalase.
4. Use a spectrophotometer to collect and evaluate results from the catalase experiment.
5. Construct proper graphs using Excel.
6. Practice scientific writing through reporting of experimental design and results.
INTRODUCTION
Enzymes are biological catalysts that increase the rate of chemical reactions by lowering the activation energy needed for
these reactions to proceed. They help carry out thousands of chemical reactions at a rate of up to 1,000,000 times that
of the same reaction without the enzyme present. As such, they are vital to the complex metabolic processes of living
cells.
Figure 6: Activation energy for uncatalyzed and catalyzed reactions
https://openstax.org/books/biology-2e/pages/6-2-potential-kinetic-free-and-activation-energy
Enzymes are generally large globular proteins made up of several hundred amino acids. They
are often associated with a non-protein prosthetic group that is important in the catalytic
function of the enzyme. Enzymes act on substances called substrates to produce one or more
products. A substrate could be a small molecule such as a sugar or lipid, or a large macromolecule
such as a protein or nucleic acid. Substrates will bind to an active site forming an enzyme-substrate
complex, held together by non-covalent bonds such as hydrogen bonds, hydrophobic interactions,
or ionic bonds. If there is a prosthetic group present, it will form part of the active site. The
substrate may undergo one or several changes (which may involve covalent bonds) before it is
converted to the final product and released into solution.
,BIO 183 / BIO183 Lab 2 Unit 2
Figure 7: Enzyme structure showing active site, substrate, and products
https://openstax.org/books/biology-2e/pages/6-5-enzymes
The enzyme itself is then free to engage with another substrate. In this way enzymes are recycled and may undergo
thousands of chemical conversions at relatively low concentrations within cells. If a substance binds to and blocks the
active site, it will interfere with the activity and efficiency of the enzyme. These substances can bind irreversibly, shutting
down the enzyme permanently, or reversibly, meaning they will dissociate under the appropriate environmental
conditions. These substances are called inhibitors.
Enzymes often bind only to certain molecules or regions on larger molecules. This property, specificity, allows the
thousands of different enzymes to perform differing functional roles. Sucrase, for instance, binds only to the
disaccharide sucrose, while another, elastase, binds only to regions on a protein where certain non-polar amino acids are
located. The concentration of the substrate will have an effect on the activity of the enzyme too. The structure of an
enzyme can be affected by environmental conditions. pH, temperature, and the concentration of salt and other small
molecules can affect the activity of an enzyme, either slowing or speeding its rate. Physical alteration can also denature a
protein, meaning conditions have sufficiently altered the structure of the protein such that it can no longer function as
an enzyme.
In lab today, we will explore the properties of enzymes. First, we will use a simple qualitative test to explore a variety of
environmental conditions on enzymes. Then, we will apply what we learn to run a quantitative test for enzyme activity
and design experiments to further study these environmental effects.
ACTIVITY 1: A QUALITATIVE STUDY OF CATALASE ACTIVITY
In this exercise, we will explore the activity of the enzyme catalase which occurs naturally in the cells of many plants,
animals, fungi, and bacteria. Catalase accelerates the breakdown of hydrogen peroxide (H2O2), a common by-product of
oxidative metabolism, into water and oxygen. This catalase-mediated reaction is extremely important to cells because it
prevents the accumulation of hydrogen peroxide, a strong oxidizing agent that can be harmful as concentrations build
up. Your instructor prepared an enzyme solution by cutting a potato into 8-10 pieces and putting them in a blender with
600 mL of cold dH2O. The potato was
blended for about 30 seconds and then filtered through four layers of cheesecloth. The filtered solution was then placed
on ice. This solution contains many cellular extracts from the potato; catalase is just one of the many enzymes in this
solution.
The basic catalase reaction:
You can tell if this reaction is occurring if you can see 02 gas (small bubbles) rise and collect as foam at the top of the
solution in the test tube. You may need to wait a few minutes to see this and hold the test tube against a dark
background.
, BIO 183 / BIO183 Lab 2 Unit 2
PROCEDURE A: TESTING THE ACTIVITY OF CATALASE
Since we do not have the option of manipulating laboratory equipment this semester, we are asking you to
read the following procedures and to pretend that you ran these experiments yourself. Results for each
procedure are displayed on the laboratory website.
Please highlight all your answers with a yellow background or use a different color font that is easy to read.
1. Before you begin this experiment, look at the components for each test tube in Table 2 below and fill in columns 1 and
2.
2. Label your test tubes 1-4. Add the first component to each of the tubes.
3. Add 5.0 mL of H2O2 to tube 1 and observe carefully for 5 minutes. Record your results in column 3 in Table 2 below,
before moving onto tubes 2, 3, and 4. Be sure to swirl your tubes to mix all the components together. Record your
results for each tube initially and check them frequently over the next 5 minutes. Record any differences that you can
see and briefly explain why you are seeing these results in column 3. Keep these tubes as reference while you move onto
Procedure B.
Please, refer to the following pictures to answer questions related to procedure A (Ctrl + Click on pictures below or visit
the laboratory website for higher resolution images)
Table 2. General catalase experimental tests performed by all groups of students.
Column 1: Column 2: Column 3:
Tube # Contents What is being What do you think What happened?
tested here? will happen?
Why?
1mL H2O + 5.0mL 3% H2O2 Reaction between There is no enzyme There was no
water and hydrogen so there probably reaction and this
1
peroxide, testing a will not be a tube acted as our
control reaction control
¼ x ¼” potato cube + 5.0mL Reaction between The potato will act A small reaction
3%H2O2 potato cube and as a catalase so a occurred between
2
hydrogen peroxide, small reaction will the potato and
testing to see if the occur peroxide, enzyme
potato will catalyze was not readily
the reaction available
Exploring Properties of Enzymes
LEARNING OBJECTIVES
1. Define the properties and role of enzymes in biological systems.
2. Evaluate data and construct an argument for why the activity of the enzyme changes under multiple experimental
conditions.
3. Design an experiment to determine the effects of various experimental conditions on the enzyme catalase.
4. Use a spectrophotometer to collect and evaluate results from the catalase experiment.
5. Construct proper graphs using Excel.
6. Practice scientific writing through reporting of experimental design and results.
INTRODUCTION
Enzymes are biological catalysts that increase the rate of chemical reactions by lowering the activation energy needed for
these reactions to proceed. They help carry out thousands of chemical reactions at a rate of up to 1,000,000 times that
of the same reaction without the enzyme present. As such, they are vital to the complex metabolic processes of living
cells.
Figure 6: Activation energy for uncatalyzed and catalyzed reactions
https://openstax.org/books/biology-2e/pages/6-2-potential-kinetic-free-and-activation-energy
Enzymes are generally large globular proteins made up of several hundred amino acids. They
are often associated with a non-protein prosthetic group that is important in the catalytic
function of the enzyme. Enzymes act on substances called substrates to produce one or more
products. A substrate could be a small molecule such as a sugar or lipid, or a large macromolecule
such as a protein or nucleic acid. Substrates will bind to an active site forming an enzyme-substrate
complex, held together by non-covalent bonds such as hydrogen bonds, hydrophobic interactions,
or ionic bonds. If there is a prosthetic group present, it will form part of the active site. The
substrate may undergo one or several changes (which may involve covalent bonds) before it is
converted to the final product and released into solution.
,BIO 183 / BIO183 Lab 2 Unit 2
Figure 7: Enzyme structure showing active site, substrate, and products
https://openstax.org/books/biology-2e/pages/6-5-enzymes
The enzyme itself is then free to engage with another substrate. In this way enzymes are recycled and may undergo
thousands of chemical conversions at relatively low concentrations within cells. If a substance binds to and blocks the
active site, it will interfere with the activity and efficiency of the enzyme. These substances can bind irreversibly, shutting
down the enzyme permanently, or reversibly, meaning they will dissociate under the appropriate environmental
conditions. These substances are called inhibitors.
Enzymes often bind only to certain molecules or regions on larger molecules. This property, specificity, allows the
thousands of different enzymes to perform differing functional roles. Sucrase, for instance, binds only to the
disaccharide sucrose, while another, elastase, binds only to regions on a protein where certain non-polar amino acids are
located. The concentration of the substrate will have an effect on the activity of the enzyme too. The structure of an
enzyme can be affected by environmental conditions. pH, temperature, and the concentration of salt and other small
molecules can affect the activity of an enzyme, either slowing or speeding its rate. Physical alteration can also denature a
protein, meaning conditions have sufficiently altered the structure of the protein such that it can no longer function as
an enzyme.
In lab today, we will explore the properties of enzymes. First, we will use a simple qualitative test to explore a variety of
environmental conditions on enzymes. Then, we will apply what we learn to run a quantitative test for enzyme activity
and design experiments to further study these environmental effects.
ACTIVITY 1: A QUALITATIVE STUDY OF CATALASE ACTIVITY
In this exercise, we will explore the activity of the enzyme catalase which occurs naturally in the cells of many plants,
animals, fungi, and bacteria. Catalase accelerates the breakdown of hydrogen peroxide (H2O2), a common by-product of
oxidative metabolism, into water and oxygen. This catalase-mediated reaction is extremely important to cells because it
prevents the accumulation of hydrogen peroxide, a strong oxidizing agent that can be harmful as concentrations build
up. Your instructor prepared an enzyme solution by cutting a potato into 8-10 pieces and putting them in a blender with
600 mL of cold dH2O. The potato was
blended for about 30 seconds and then filtered through four layers of cheesecloth. The filtered solution was then placed
on ice. This solution contains many cellular extracts from the potato; catalase is just one of the many enzymes in this
solution.
The basic catalase reaction:
You can tell if this reaction is occurring if you can see 02 gas (small bubbles) rise and collect as foam at the top of the
solution in the test tube. You may need to wait a few minutes to see this and hold the test tube against a dark
background.
, BIO 183 / BIO183 Lab 2 Unit 2
PROCEDURE A: TESTING THE ACTIVITY OF CATALASE
Since we do not have the option of manipulating laboratory equipment this semester, we are asking you to
read the following procedures and to pretend that you ran these experiments yourself. Results for each
procedure are displayed on the laboratory website.
Please highlight all your answers with a yellow background or use a different color font that is easy to read.
1. Before you begin this experiment, look at the components for each test tube in Table 2 below and fill in columns 1 and
2.
2. Label your test tubes 1-4. Add the first component to each of the tubes.
3. Add 5.0 mL of H2O2 to tube 1 and observe carefully for 5 minutes. Record your results in column 3 in Table 2 below,
before moving onto tubes 2, 3, and 4. Be sure to swirl your tubes to mix all the components together. Record your
results for each tube initially and check them frequently over the next 5 minutes. Record any differences that you can
see and briefly explain why you are seeing these results in column 3. Keep these tubes as reference while you move onto
Procedure B.
Please, refer to the following pictures to answer questions related to procedure A (Ctrl + Click on pictures below or visit
the laboratory website for higher resolution images)
Table 2. General catalase experimental tests performed by all groups of students.
Column 1: Column 2: Column 3:
Tube # Contents What is being What do you think What happened?
tested here? will happen?
Why?
1mL H2O + 5.0mL 3% H2O2 Reaction between There is no enzyme There was no
water and hydrogen so there probably reaction and this
1
peroxide, testing a will not be a tube acted as our
control reaction control
¼ x ¼” potato cube + 5.0mL Reaction between The potato will act A small reaction
3%H2O2 potato cube and as a catalase so a occurred between
2
hydrogen peroxide, small reaction will the potato and
testing to see if the occur peroxide, enzyme
potato will catalyze was not readily
the reaction available
