Biology 12 – Unit 2
Name ___________________________________
Lab – The Effect of Temperature on Enzyme Activity
Background
Some fruits contain enzymes capable of hydrolyzing proteins. If you are hoping to
tenderize a steak, the enzymes found in papaya can be helpful. However, not all enzymes found
in fruit can be helpful all the time. The enzyme Actinidin found in fresh kiwi fruit is capable of
hydrolyzing proteins found in dairy products. As the milk proteins are digested acids are
released and the food ends up having a very unpleasant bitter taste.
Pineapple contains a digestive enzyme called bromelain which is capable of breaking
down the proteins such as gelatin – the main ingredient in Jell-O. Gelatin is a processed version
of the protein collagen, a simple protein that makes up one-third of all proteins in the human
body. The main source of the collagen that is used in Jell-O comes from hooves, bones,
connective tissue found on cows, horses and pigs. Along with collagen, Jell-O consists of water,
food coloring, sugar, and artificial flavours. Collagen is found in all living animals. This protein is
what gives body parts strength, flexibility, and protection. There are five major categories of
collagen that range from the fibres in your eyes to the structure of placentas. To harvest the
collagen needed for gelatin the Jell-O Corporation turns to natural sources found in cows,
horses, and pigs. The animals' body parts which were previously mentioned are ground up to
expose the proteins within. After they are ground up the bio matter is then treated with a strong
acid or base, which breaks down the cellular structures of the collagen to release the proteins
from connective tissue. Once the proteins become separated from the tissues the bio-mass is
then discarded. Then, the mixture created from the released proteins (collagen proteins, which
are the basis of Jell-O) and the strong acid or base is boiled.
Bromelain is used in many meat tenderizers for this purpose (cooking ham with
pineapple makes it tender). If you have ever read the directions on a Jell-O package, then you
will have seen that it warns you not to put pineapple chunks into the Jell-O. This is because JellO is a protein mesh with trapped pockets of liquid and the bromelain cuts the protein chains and
keeps the gelatin from gelling properly.
Pineapple plants produce this enzyme as a self-defence mechanism. The sap of the
pineapple plant contains much higher concentrations of bromelain and can cause severe pain if
eaten.
Purpose:
Today we are going to use fresh, frozen, and canned pineapple to see how changes in
temperature can affect bromelain’s ability to digest the protein gelatin.
Materials:
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4 test tubes
Hot JELL-O
Fresh pineapple
Canned pineapple
Frozen pineapple
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Knife
Sharpie
Beaker with ice water bath
Weigh Boat
Electronic Balance
1
Biology 12 – Unit 2
Name _______________________________
Procedure
1. Using your knowledge of how enzymes function, record a hypothesis that
predicts the results of this lab investigation for EACH of your test conditions.
2. Label 4 test tubes with the numbers 1-4.
3. Prepare an ice water bath in a beaker.
4. Select pieces of fresh, canned and frozen pineapple that are approximately equal sizes. The
pieces should be just small enough to slide into your test tubes.
5. Using the electronic scale, weigh your smallest piece and record its mass below. Weigh and
trim the other pieces as necessary so that each piece has the same mass measured to one
decimal place. ** Do this quickly so your frozen pineapple doesn’t melt too much!
Type of Pineapple
Mass
_________________ - ____________ g
_________________ - ____________ g
_________________ - ____________ g
6. Gently mash each piece of pineapple in the weigh boat to increase the surface area where
bromelain can react with the gelatin molecules in the Jell-O.
7. Place your pineapple pieces and any juices that are in the weigh boat into their corresponding
test tubes:
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Test
Test
Test
Test
tube
tube
tube
tube
#1
#2
#3
#4
–
–
–
–
Control (Jell-O only, no pineapple)
Fresh Pineapple
Frozen Pineapple
Canned Pineapple
8. Using a graduated cylinder add 20 mL of liquid Jell-O to each test tube.
9. Gently mix the contents of the tubes by rolling them upright between the palms of your
hands.
10. Place all four test tubes into an ice water bath in your beaker.
11. While you are waiting for the Jell-O to set, complete the data table as part of your results
section for this lab.
12. Every 2 minutes check to see if the Jell-O is setting in the tubes. When test tube #1
(control) has set 100% the experiment is over. Record your observations in your table.
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Biology 12 – Unit 2
Name _______________________________
Results:
Table 1. Percent solidification of Jell-O over time
Time (mins)
0
2
4
6
8
10
12
14
16
18
20
Test Tube #1
Control
Test Tube #2
Fresh
Test Tube #3
Frozen
Test Tube #4
Canned
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Biology 12 – Unit 2
Name _______________________________
Formal Lab Write-Up Assignment
Total
/26 marks
Once you have completed your experiment write up a formal lab report. Follow instructions carefully!!
Writing a proper lab report is an important skill to learn.
Your lab report must be typed, double-spaced and include:
1 marks
Your name, date, lab partners, title etc.
1 mark
Purpose - Why are we doing this lab?
2 marks
Hypothesis - Make an educated guess about the results of this lab. Make sure
to include hypotheses for each test condition. Do not attempt to provide reasons
for your hypotheses, simply state them i.e. "If _____[I do this] _____, then
_____[this]_____ will happen."
1 mark
Materials – List out the materials used in this lab.
1 mark
Procedure - (Simply refer to the procedure in this lab – DO NOT write it out)
7 marks
Results -
(2 marks)
1) Data Table - proper format all relevant information included
Mass of pineapple pieces and any other observations made
2) Graph - title, X and Y axis labels, legend, 4 lines, appropriate scale
If you do not have excel – use this link to create a graph:
http://nces.ed.gov/nceskids/createagraph/default.aspx
3) Data sheet that you made any other observations or records of data. Will be stapled
to back of report.
(5 marks)
10 marks
Discussion - (paragraph form, double spaced – DO NOT simply answer the
questions, discuss what you have learned and show me that you can apply your
knowledge)
Things to include in your discussion:
(1 mark)
Discuss why we used a control in this experiment.
(4 marks)
Summarize your observations for each test condition in the lab. Use the
information in your notes about how temperature affects enzyme activity to
explain what you observed for each condition. ** This is most effectively done if
you write a paragraph that explains each test condition.
(5 marks)
Were your results for each condition what you had hypothesized? Why or why
not? Explain. Consider this as you interpret your results: Do you think our
experimental set-up had any influence on the results for any of the test
conditions?
3 marks
Conclusion
(2 marks)
Was there evidence to support or reject each of your hypotheses? Explain while
summarizing what you have learned about the effects of temperature on enzyme
activity.
(1 mark)
Provide an example of how you could apply this newly learned knowledge in the
future.
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Biology 12 – Unit 2
Name _______________________________
The Effect of Temperature on Enzyme Activity
Supplementary Questions
/10 marks
1. Why did test tube #1 only contain JELL-O e.g. explain the importance of a control? 1
mark
2. The process of canning involves exposing the pineapple to high temperatures for
extended periods of time. How does this process change bromelain? 1 mark
3. Check out the following website:
http://www.sciencebuddies.org
Look around this website to help you answer the following question.
List and describe the steps involved in scientific method. 4 marks
5
Biology 12 – Unit 2
Name _______________________________
4. You hypothesize that the hormone thyroxin will increase the heart rate of mice. Use
the following materials; design a controlled experiment to test this hypothesis. The
design will require that you have a purpose, hypothesis, materials, and procedure
(how you would carry it out). Please do not go any further. We do not need to
expose mice to any unnecessary testing.
For this experiment you acquire the following materials:
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A population of 30 mice
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2 Identical cages to house the mice
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Food with thyroxin and food without thyroxin
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Heart rate monitors
4 marks
(answer by typing up on the computer and printing it out. Please remember to
double space.)
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Biology 12 – Unit 2
Name _______________________________
The Effect of pH on Enzyme Activity
Background
Extremes in pH levels, like temperature, cause alterations in the structure, and thus the function, of
enzyme molecules. Also, varying concentrations of pH levels in solution affect the activity of the
enzyme. In groups you will test the effect of different concentrations of an acid (HCl) or a base
(NaOH) on the activity of the enzyme Bromelin.
MATERIALS PER GROUP:
(Group A will need 1 ml HCl, Group B will need 1 ml NaOH)
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21 test tubes
10 ml graduated cylinder
10 - 5 ml pipettes
test tube rack
water
30 ml frozen pineapple juice concentrate, thawed
1 pkg Knox gelatin, prepared according to instructions on the package.
PROCEDURE:
1. GROUP A: Label 10 test tubes A-1, A-2, A-3, etc. up to A-10.
GROUP B: Label 10 test tubes B-1, B-2, B-3, etc. up to B-10.
2. Carefully measure 3 ml pineapple juice into each of the labeled test tubes.
3. Place 9 ml water into the 10 empty test tubes. Label one of these tubes as CONTROL and set
it aside.
4. Make a serial dilution in the 9 test tubes by following the dilution table drawn below.
Group A use HCl, Group B use NaOH. *** Use a different pipette for each dilution.
5. Transfer 3 ml of diluted pH concentrations into each test tube of pineapple juice, using the
dilution table below as a guide. Record the concentration of solution placed in each test tube.
(Example: A-1 = 1:1 dil, A-2 = 1:10 dil, A-3 = 1:100 dil, etc.) The solution concentrations
become weaker as the test tube numbers progress from 1 - 9.
6. Transfer 3 ml of water from CONTROL tube into tube A-10 (or B-10).
7. Add 10 ml gelatin to each test tube, A-1 to A-10 (or B-1 to B-10). Shake well being careful not
to let the acid or base come into contact with skin.
8. Refrigerate test tubes overnight.
9. On day 2, check each test tube for liquidity of the contents. Record observations.
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Biology 12 – Unit 2
Name _______________________________
ANALYSIS:
1. At what concentration of acid or base was the first signs of liquidity observed?
2. What conclusion can be derived as to the acid/base concentration at which bromelin's
molecular structure is altered?
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