Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
ENZYME LAB
Introduction:
Inside our bodies many different chemical reactions occur at the cellular level which
maintain life. One such reaction is called decomposition reaction. A decomposition
reaction is a type of chemical reaction in which a substance degrades (breaks down) into
two or more basic components. Decomposition reactions often require exposure to a
catalyst, such as a heat source or solvent. A simple example of such a breakdown is the
conversion of water (H2O) into hydrogen (H2) and oxygen (O2) gas via a process known
as the electrolysis of water. Decomposition reactions requiring a catalyst are called
catalytic decomposition reactions.
A catalyst is a substance which alters the rate of a chemical reaction but is chemically
unchanged at the end of the reaction. It is possible to divide catalysts into two groups –
inorganic catalysts and organic (biological) catalysts. Inorganic catalysts can be a pure
element; e.g. Platinum, Nickel; or it could be a pure compound, e.g. Silica, Iron III
Oxide; it could be dissolved ions, e.g. Copper ions, Cobalt II ions; or it could be a
mixture, e.g. Iron-Molybdenum. Biological catalysts are called enzymes. Most enzymes
are protein molecules (though recent research indicates that nucleic acids have enzymatic
capacities), and they specifically catalyze only one reaction. Without them chemical
reactions would be too slow to maintain life.
For this lab you will observe reactions using a variety of substances and the liquid
hydrogen peroxide (H202). You will be using calf liver as your source of an enzyme
whose function is to destroy H202 (breaking it down to water and oxygen gas) which is
formed as a by- product of certain natural chemical reactions in the body, but which is
also highly toxic. Without a reliable and steady supply of this enzyme in the body, H202
would be deadly! Because we rely on this enzyme so much, we are quite interested in
how it works, and in what controls its activity.
Purpose:
In this lab you will investigate the ability of several substances to catalyze the
decomposition of hydrogen peroxide and become familiar with some of the
characteristics of enzymes.
Carry out the procedure below and write up a report of this experiment answering
the questions given.
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Module 11
Materials:
Enzyme Lab
hydrogen peroxide - 3% approx.
copper metal
raw fresh potato
calf liver
MnO2 powder
beaker
Completed By: Suzette McLean-Fletcher
hot plates
thermometer
candle, matches
test tubes
mortar and pestle
applicator sticks (splints)
Procedure:
1.
2.
3.
4.
Clean 8 large test tubes.
Number the test tubes from #1 to #8 and place in a suitable rack.
Add approximately 4 mL of hydrogen peroxide to each test tube.
Carefully add the following to the test tube and record ALL results:
#1.
nothing (do you really need to do this one???)
#2.
a pinch of manganese dioxide
#3
a small piece of copper
#4.
a piece of liver (10 mm X 10 mm x 10 mm)
#5.
crushed liver, the same size as in #4
#6.
boiled liver (5 min.), same size as in #4
#7.
fresh potato, same as in #4
#8.
A small pinch of catalase (if available)
5. Record the temperature of the hydrogen peroxide before and after adding the pieces
of liver (crushed and raw).
6. Repeat #4, adding raw liver and test to determine if the gas evolved is something you
know??? Do a splint test.
7. Clean up your equipment, clean our foreign matter from the sinks!!!!!
Safety Instructions:
1. Wear a glove at all times
2. Carry out the different instructions in procedure 4 one at a time. Record results
before moving on the next reaction.
3. Do not put your face over the test-tubes. Stand some distance away … but not too
far that you cannot see the reaction properly!
4. Use a test-tube holder to hold test-tubes.
5. DO NOT play in the lab.
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Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
Results: ( Below are the possible results/descriptions)
Table showing observations for the decomposition reactions of hydrogen peroxide.
Test-Tube#
/Added
substances
I (nothing)
2 (Manganese
dioxide)
3 (piece of
copper)
4 (piece of
liver)
5 (crushed
liver)
6 (boiled
liver)
7 (fresh
potato)
8 ( catalase)
Reaction/Observations
nothing
Instant vigorous reaction.
Frothy/foamy bubbles produced
Frothy/foamy bubbles produced
but reaction not as quick as testTube 2. Reaction not as vigorous
Frothy/foamy bubbles produced
but reaction not as quick as testTube 2. Reaction took slightly
longer to start than test-tube 3
but eventually more vigorous
than test-tube 3
Instant vigorous reaction.
Frothy/foamy bubbles produced
overflowing the test-tube. More
vigorous than test-tube 2
Temperature
(test-tube 4 &5)
Before addition- ~
25ºC
Splint Test
Glowing splint
re-lighted
After addition~30 ºC
(these values are
hypothetical)
Before addition25ºC
After addition- 40
ºC
(these values are
hypothetical)
No reaction
Similar to test-tube 4.
Frothy/foamy bubbles produced
but reaction not as quick as testTube 2. Took longer to start than
test-tube 4. And not as vigorous
Instant very vigorous reaction as
test-tubes 2 & 5. Frothy/foamy
bubbles produced
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Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
Discussion Questions
1. Rank the reactions for #1 to #8 using a scale that shows the varying rates of reactions
that you observed. (1 to 5) (A B..F) (none….wild)
2. Is MnO2 an enzyme? Is it a catalyst? How could you prove if it is a catalyst?
3. Write a balanced equation for the decomposition of hydrogen peroxide.
4. How could you prove if the enzyme in liver is reusable?
5. Try to determine the name of the enzyme in liver cells that is capable of decomposing
hydrogen peroxide.
6. What is denaturation? Did it happen in this lab? What are other ways to denature an
enzyme?
7. Is the reaction exothermic or endothermic? How do you know?
8. Prepare a simple procedure that could be followed to show the effect of temperature
on the rate of enzyme activity?
BONUS: What are some applications of enzymes?
Expected Discussion.
The reaction is a decomposition reaction where hydrogen peroxide is broken down into
water and oxygen. This reaction occurs naturally but is very slow and can be speeded up
using catalysts. A catalyst lowers the activation barrier of a reaction so that less energy is
needed to break reactant bonds in order to initiate a reaction. Therefore, the reaction takes
less time because more molecules possess the needed minimum energy necessary for a
reaction .The reaction is:
2 H2O2 (aq) ===> 2 H2O (g) + O2 (g)
1. The reactions ranged in intensity from no reaction to instant, very vigorous/ wild
reactions. On a scale of 1-5 where 1 is no reaction and 5 is very vigorous/wild
reaction then:
Test tubes #1 and 6 would be….. 1
Test-tube #7………………………2
Test-tube # 3 & 4 …………………3
Test-Tube # 5………………………4
Test-Tubes # 2 and 8………………5
Test-tube 1 was the control experiment. This is important because it provides a standard
against which the reactions can be compared. It is opposite in reaction to test-tube 8.
Test-tubes 2 and 3 showed the effect of inorganic catalysts as well as concentration of
these catalysts.
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Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
Test-tubes 4, 5,& 7 showed the effect of enzyme concentration on a reaction. The
crushed liver resulted in the cells membranes being destroyed making the enzyme readily
available ( high concentration) unlike the whole liver piece where the cell membranes are
intact so enzyme is not readily available(low enzyme concentration). Also for the potato
the cell membrane adds another barrier to the availability of the enzyme so that is why
the reaction was much slower (hydrogen peroxide had to diffuse across cell membrane
and cell wall of potato cells).
Test-tube 6 showed the effect of temperature on enzyme reaction. High temperature
destroys /denatures enzyme rendering them inactive- so no reaction occurred.
2. Manganese dioxide (MnO2) is an inorganic catalyst. It is not an enzyme as it is an
inorganic compound- enzymes are organic compounds/catalysts. To prove it is a
catalyst you could carry out an experiment that would occur normally. The
experiment would be done with and without MnO2. The reaction would occur
faster when MnO2 is added. This would prove it is a catalyst.
3. Balanced equation for the decomposition of hydrogen peroxide is
2 H2O2 (aq) ===> 2 H2O (g) + O2 (g)
4. To prove if the enzyme in liver is reusable you could do the following: After the
initial reaction in test-tube 5 is finished remove some of the crushed liver and
place it into another clean test-tube. Add some hydrogen peroxide to it. If reaction
occurs again then it is reusable.
5. The name of the enzyme in liver capable of decomposing hydrogen peroxide is
catalase.
6.
Denaturation is the change in the three-dimensional structure of an enzyme or
any other soluble protein, such that it is rendered inactive. Denaturation of the
enzyme did occur in this lab. When the liver was boiled (test-tube 6) for 5 minutes
the heat effectively destroyed/changed the 3D structure of catalase thus rendering
it inactive so that’s why there was no reaction. Other ways to denature an enzyme
is to use/ put it in chemicals such as acids and alkalis.
7. The reaction was exothermic- i.e. energy was released. This is so because there
was an increase in temperature of the hydrogen peroxide after the reaction when
tested in test-tubes 5 and 6.
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Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
8. Simple procedure that could be used to show effect of temperature on the rate of
enzyme activity.
Working in groups of 2 or 4:

Using Styrofoam cups and corrugated cardboard paper or newspaper, set up an
ice bath (0oC or as close to this as possible using ice and water), a room temp
water bath, a 37 oC bath and a water bath of temperature greater than 80 oC.

Place 40 ml 3% H2O2 in each of 4 test-tubes. Place 1 test-tube in each of the 4
water baths and allow them to incubate for 5 minutes. (DO NOT BOIL
HYDROGEN PEROXIDE!!)

Crush some fresh beef liver, add a little water to make a solution.

Cut small square pieces of filter paper (1cm x1cm) and soak them into the crushed
liver solution for 2 minutes.

Using a forceps, place a square of filter paper in each incubated test-tube. It will
fall to the bottom of the test-tube. Note the time it takes for the filter paper to rise
to the top of the hydrogen peroxide solution.

Record your data in an appropriate table.
Conclusion:
The decomposition of hydrogen peroxide can be catalyzed by organic and inorganic
catalysts. There are factors that affect the activity of enzymes such as enzyme
concentration and temperature. The higher the enzyme concentration the faster the rate of
reaction. High temperature denatures enzyme rendering them inactive. These factors
affecting enzymes translates to the characteristics of enzymes.
Some Applications of Enzymes:
Stickies Removal
Enzymes are used by the pulp and paper industry for the removal of glues, adhesives and
coatings that are found on paper during recycling of paper.
Detergents
Enzymes are used in laundry detergents to degrade proteins that cause stains such as
grass, red wine and soil stains. Enzymes (lipases) are also used to dissolve fat stains and
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Module 11
Enzyme Lab
Completed By: Suzette McLean-Fletcher
clean grease traps. Currently, a popular area of research is the investigation of enzymes
that can tolerate, or even have higher activities, in hot and cold temperatures.
Textiles
Enzymes are now widely used to prepare the fabrics that your clothing, furniture and
other household items are made of.
Foods and Beverages
Biotechnology has made it possible to isolate and characterize the specific enzymes
responsible for these processes. Enzymes are used to make cheese, alcohol, wines, beers
and other brews, coffee, tea, dietetics, etc. It has allowed the development of specialized
strains for specific uses that improve the flavour and quality of each product. Enzymes
can also be used to make the process cheaper and more predictable, so a quality product
is ensured with every batch brewed. Other enzymes reduce the length of time required for
aging, help clarify or stabilize the product, or help control alcohol and sugar contents.
Medicine
There are many uses of enzymes in medicine. For example:

preventing excessive blood clotting
and reducing the tendency for platelets and red blood cells to ‘clog’

diagnosis of disease; this is because if enzymes are present where they should
not be then something may be wrong. An example of this is in the case of a
damaged liver. Enzymes that would be normally found in the liver, leak into
the blood
stream. By testing the blood for alternate enzyme activity liver
damage can be confirmed.

detecting and measuring amounts of glucose in blood

manufacturing of drugs: where the synthesis of drugs is difficult enzymes are
used to perform the chemical procedure.
References:
1.
2.
3.
4.
http://www.wisegeek.com/what-is-a-decomposition-reaction.htm
http://www.purchon.com/chemistry/catalyst.htm
http://www.sciencegeek.net/Chemistry/chempdfs/PeroxideCatalysis.pdf
http://www.ecb.org/guides/pdf/Science_Key_Concepts/SKC_REACTIONS_AN
D_ENERGY_CHANGES.pdf
5. http://biotech.about.com/od/whatisbiotechnology/a/EverydayEnzymes.htm
6. http://www.123helpme.com/use-of-enzymes-in-medicine-view.asp?id=150313
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