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A MYSTERY UNFOLDS--PROTEIN STRUCTURE AND FUNCTION
MASTER TEACHER Veronica Zonick
GRADES 9-10
OVERVIEW
This two-day lesson provides students with an understanding of
how a protein's structure affects its function inside and outside of the cell.
In this lesson, students will model the primary sequence of proteins, and their
folding into secondary and tertiary structures. The use of video and three
dimensional manipulatives are intended to address the learning styles of both
visual- and tactile/kinesthetic-oriented students. Additionally, students will
use an inquiry approach to explore the effects of temperature and pH on enzyme
kinetics. Students will pool and graph their data to produce a
kinetics plot that shows the temperature- and pH-dependent activity of a
typical enzyme.
ITV SERIES
Cell Biology Resource:
World of Chemistry: Protein Structure and Function
LEARNING OBJECTIVES
Students will be able to:
*Model how amino acids link to form polypeptide chains,
and show how these chains fold into particular 3 dimensional shapes.
*Show how an enzyme brings reactants together, to change the
speed of the reaction.
*Graph enzyme activity under different conditions.
MATERIALS
(Per class)
1 lb container of chicken livers
One 16 oz container of fresh hydrogen peroxide (available at
pharmacies)
Paper towels
One can of pineapple chunksOne fresh pineapple, cut into chunks
Three large boxes of gelatin dessert (any flavor), prepared and
divided
(Per student)
2 Paper cups
Toothpick
Pen or pencil
Handout:
1 sheet graph paper
1 sheet notebook paper
1 chenille stem (pipe cleaner), knotted at one end
30 pony beads in assorted colors
1 pair of safety glasses/goggles
(Per pair of students)
triple-beam or digital balance (scale)
thermometer
Mortar and pestle
Two test tubes plus rack
transfer pipet
metric ruler
2 colored cellulose expanding sponges
VOCABULARY
amino acid
tertiary structure
polypeptide
catalyst
peptide bond
enzyme
primary structure
substrate
secondary structure
PRE-VIEWING ACTIVITIES
The day before class, prepare gelatin dessert, according to the
manufacturer's directions. Prepare three large boxes of gelatin per class
of 30 students. Dispense approximately 2 tablespoons of gelatin into each
cup, and chill. At the start of class, place these cups on a lab table and ask
the students to pick up 2 cups of gelatin, a piece of fresh pineapple and a
piece of canned pineapple on their way into the classroom.
As class begins, ask your students to add a chunk of fresh
pineapple to one cup, and a chunk of canned pineapple to the other cup.
Direct students to set the cups aside for the next 20 minutes. Tell your
students, "We are going to do a quick experiment with the gelatin and
pineapple. The pineapple and gelatin both contain molecules that can react
with each other. "Ask your students to brainstorm on the following
question, "What molecule do the gelatin and pineapple have in common?"
Write all answers on the overhead or chalkboard. Because both of these
foods came from living things, (the pineapple from a plant, and the gelatin from
animal bones), both should contain four biomolecules (DNA, RNA,
carbohydrates, fats and proteins) Tell your students, "One
thing that the pineapple and gelatin have in common is that they are rich in
protein. The protein in gelatin makes it rubbery, and the protein in
pineapple attacks your tongue if you eat too much of it. Today we are going to
look at two things that make proteins so special that every living thing depends
on them for survival. We are going to look at how they are put together,
and the amazing way they work in your cells."
FOCUS FOR VIEWING
Pass out a sheet of paper to your students. Tell your
students, "Proteins are giant molecules that are made of many smaller
pieces. You are going to watch a video that shows how these parts fit
together. " To give students a specific responsibility while viewing,
say, "Listen for the name of the building blocks that make up protein.
Write down three of the examples of these building blocks."
VIEWING ACTIVITIES
Cell Biology Resource: 102 Molecular Building Blocks
Begin tape where the video shows the words "Protein
Structure." The audio following this screen is "When you
look at an animal, just about everything you see is made of protein."
To allow students an opportunity to record three types of amino acids, pause
the tape at the end of the computer animation of the amino acid chain forming a
helical shape. Audio is "and one to several polypeptides form a
protein. " Rewind and replay this segment.
Stop tape and eject. Say, "Now that
we've seen the pieces that make up a protein, lets look at how the pieces are
organized into a particular shape." Insert the
tape, World of Chemistry: Protein Structure and Function. To give
students a specific responsibility while viewing, say, "Look for the three
ways that amino acids are arranged in every protein. Sketch these on your
paper."
Begin tape where the video shows pony beads linked
together via a cord. Audio is " The structure and function of a
protein molecule is determined by the order, the number and kind of amino acids
in the chain." Continue playing this brief segment until the audio,
"the sequence of amino acids is called the primary structure (Video is
still pony beads on a cord). Fast forward to pony beads being added
to the cord. Audio is "One by one, more amino acids are linked to
form a long chain. Many proteins have more than 100 amino acids in a
single polypeptide chain." Pause tape. Fast forward
again to an image of blue amino acids in a twisted chain. Audio is
"In the story of protein structure, the chain is merely the starting
point," Pause when an image of a blue green protein molecule
containing 5 different chains appears. Audio is "... gives a second
level of structure to the protein."
To allow students an opportunity to record these responses, rewind
tape to the image of the pony beads on a string. Pause.
Pass out an "amino acid" manipulative to each student and ask them to
follow along with the manipulative to show the different ways that a protein is
organized, as it appears on the screen. So that students can focus on
change in the molecule's shape, eliminate audio.
Pause after each level of organization is shown, to
check that all students have modeled that level of protein structure. Rewind
and replay the sequence of primary, secondary and tertiary protein sequence,
if necessary.
Tell your students, "Now that we have seen what proteins
are made of, and how they are assembled, let's look at the two proteins we put
together at the start of class. Does anyone notice a change in their cups
of gelatin?" Students who had the cup with fresh pineapple should have
liquefied gelatin, while those who had canned pineapple should have intact,
polymerized gelatin. Tell your students, "Pineapple
contains a protein called a protease which breaks down protein into amino acids.
Now let's look at how a protein can attack and break down a molecule like
gelatin. In this next video segment, we will look at another protein that
speeds up or slows down a chemical reaction. To give students a specific
responsibility while viewing say, " Listen for the name of a protein
that speeds up a chemical reaction and the chemical that this protein
modifies."
Insert tape, Cell Biology Resource 102:
Molecular Building Blocks.
Begin tape at the words, "How enzymes modify
reactions." This image is followed by the audio,
"Disinfect a cut with hydrogen peroxide..." Pause at the words
Nucleic Acids overview (No audio).
Rewind tape to the beginning of this segment.
Say, "Now that we know that an enzyme is the type of protein that speeds up
a chemical reaction, and a substrate is the molecule that is modified by the
enzyme, listen for the name of the place in the enzyme where the substrate fits
into the enzyme." Resume tape.
Pause at the image of a globular protein, with the
active site outlined. Ask a student to come to the television and locate
the active site. Use an overhead transparency marker to highlight the
image of the active site on the television screen. Say, "Now
listen to find out how the active site speeds up the reaction." (it
brings the substrates into close proximity. The closer two molecules are
the more likely it is that they will react.) Resume tape. Stop
tape at the words, Nucleic Acids Overview.
Say, Look at your gelatin cups again. Did the canned
pineapple do anything to the gelatin? (No.) Ask your students,
"What is a difference between the two types of pineapple?" (Lead
students to the observation that canned pineapple is cooked at high temperatures
to kill any microbes that may be present).
Say, "When proteins are heated, the bonds that hold
together the protein molecule begin to break. The protein molecule begins
to unfold, and it can no longer attack and break the protein, gelatin."
Say, "When the pineapple was heated, it no longer was able to break
down the gelatin. What do you think might have happened to the active
site?" (The heat caused a change in the shape of the molecule.) Ask
the students to manipulate their protein molecules to change the overall shape
of the molecule.
POST VIEWING ACTIVITIES
DAY ONE:
Pass out the manipulatives of the enzyme active site, and pass
out the instruction sheet for the activity, "Lock and Key." Have
students work in pairs to complete this activity. In this
tactile-kinesthetic activity, students will work in pairs to review the
interaction of enzyme and substrate. In this manipulative, the two smaller
pieces are the substrate gelatin, and the larger piece represents the enzyme,
protease. The perfect fit between enzyme and substrate is similar to a
lock and key. Only keys of a specific shape can fit into an enzymes active
site. Once the substrate and enzyme have come together, a change in the
shape of the enzyme can cause the substrate molecule to twist. As a
result, bonds may break, and a large molecule such as gelatin may be converted
into smaller protein fragments. Only the substrate is changed.
Therefore, one enzyme may be reused many times.
DAY TWO:
The day before this lab, purchase one 1 lb tub of fresh chicken
livers. Buy the freshest product possible. Grind half of the livers
in a food processor with an equal volume of water, and divide the resulting
slurry into dropper bottles. Chop the rest of the livers into cubes.
Store in the refrigerator. Keep on ice during the lab. At the start
of class, say, "Yesterday we looked at the structure of proteins and saw
that the shape of a protein is very important. If an enzyme has a
particular shape it fits in with its substrate and can speed up a chemical
reaction. If an enzyme gets bent out of shape, it can no longer help the
reaction occur. In yesterday's video we looked at how peroxide is
changed by enzymes in your skin. Why do people put peroxide on
cuts?" (To kill microbes) "Peroxide reacts with almost
anything it comes into contact with. It is a cell killer. Can
anyone think of a reason why it doesn't kill our cells, too?" (
Accept all responses) Say, "We have an enzyme in our body cells that
takes the peroxide and twists it until it breaks into water and oxygen."
Write the following equation on the chalkboard:
2H2O2
-------------------> 2H2O
+ O2
"The enzyme in our body takes something dangerous, and
change it into two useful chemicals. Today you are going to examine
how this enzyme works, and find out what happens when you add heat to this
enzyme." Pass out the activity, "Catalytic Converter--part
one." Direct students to the lab, where each table is set up with the
materials listed previously, under the heading "lab station."
In this activity, students will compare the enzymatic activity of two
protein-rich foods. Egg white is largely the protein albumen, whereas
liver is rich in the enzyme, catalase. Students should find that egg white
does not help break down hydrogen peroxide, while the catalase in liver
promotes a dramatic chemical change. While students are completing this
lab, ask them what they think the peroxide is changed into. Whet
students' interest by doing the flame test for oxygen: Light a
wooden splint; let it burn for 3 - 5 seconds, then blow it
out. Place the glowing end of the splint in to each test tube. If
large amounts of oxygen are being produced, the splint will burst into flame,
dramatically.
DAY THREE
Pass out the activity, Catalytic Converter-- part two. Ask
students to design an activity that tests how heat affects enzyme activity.
Students should test a range of 5 temperatures, and graph their results.
Next, pool the data, and have students construct a master graph of
catalase activity. Catalase, like most enzymes, will give a bell shaped
curve. For catalase from animal sources, the peak activity will be close
to body temperature (35-40 degrees Celsius). At extremely low
temperatures, molecules move slowly and are less likely to encounter each other.
For this reason, enzyme activity will decrease as temperature decreases.
At extremely high temperatures, most proteins unfold, or denature.
As a result, the active site is lost, and the enzyme can no longer bind to
its substrate. (Egg white provides a dramatic demonstration of heat
denaturation.) For this reason, enzyme activity will decrease at
higher temperatures.
ACTION PLAN
1. Invite a physician or medical laboratory technician to
discuss how testing a patient's enzyme levels gives an overall picture of her
health.
2. Take a virtual field trip to one or more of the
following sites on the World Wide Web:
Bugs in the News--
http://falcon.cc.ukans.edu/~jbrown/bugs.html
This site has a wealth of information about why enzymes and
molecular biology are valuable, medically and economically. It also
contains up to the minute information on such timely enzyme related topics as
protease inhibitors and AIDS.
Howard Hughes
Virtual Lab-- http://www.telefusion.com/lectures/hiband/neat/index.html
This site contains an online game where one can act as a
scientist, testing lab samples with enzymological techniques to determine
whether or not a sample is infected with a disease.
G6PD deficiency home page--
http://rialto.com/g6pd
This site is the source of information on the most common human
enzyme deficiency on earth, Glucose-6-phosphate Dehydrogenase deficiency, a
disorder that affects at least 400 million people in the world. This
disorder gives affected individuals life a threatening allergy to the Fava bean.
EXTENSIONS
NUTRITION/HOME ECONOMICS
Examine how enzymes are used in cooking meats, preparing
cheeses, wine and other foods. E-mail a chocolate producer, a supplier of enzymes to the food industry such as Vallley Enzymes,http://ValleyEnzymes.com/)
and ask them to explain how they put the liquid in chocolate covered cherries.
Hint: it involves the enzyme invertase!)
COMPUTER SCIENCE/ART
Use HyperStudio or other multimedia authoring programs to create
an interactive tutorial on protein structure and function.
Pattern for cutting enzymes and
substrate molecules out of cellulose kitchen sponges. Two sponges in
different colors are needed for each manipulative.
LAB: LOCK AND KEY.
In this lab, you will examine how an enzyme and substrate fit
together.
Refer to your textbook to help answer these questions.
1. What is an enzyme?
2. What is a substrate?
3. Obtain an enzyme model. The orange sponge
represents an enzyme, protease. The purple pieces represent the amino
acids that form the protein gelatin.
4. Fit the enzyme and gelatin molecules together like a
jigsaw.
5. How is the shape of the enzyme similar to the shape
of the gelatin?
6. In real life, an enzyme and its substrate fit
together perfectly. The enzyme is a perfect match for the gelatin.
What part of the enzyme matches the shape of the gelatin?
7. How are the enzyme and substrate like a lock and
key?
10. Once the gelatin molecules have been broken apart,
the enzyme releases them. Release the new molecules from your model.
11. Which has been changed-- the enzyme or the
substrate? Which stays the same?
12. Based on your answer to number 11, can an enzyme be
reused, or are they disposable? Explain your reasoning.
CATALYTIC CONVERTER-- PART ONE
Hydrogen peroxide is a cell killer. For this reason,
cells have an enzyme called catalase, which takes peroxide (H2O2)
and breaks it down into oxygen (O2)
and water (H2O):
H2O2catalase
> H2O + O2
In this lab, you will examine how enzymes work.
1. What are enzymes made of?
2. What is a catalyst?
3. Obtain two test tubes. Measure out 3ml of
hydrogen peroxide for each test tube. Add one drop of detergent to each
tube.
4. To the first tube, add 20 drops of egg white.
Observe any changes. Measure the amount of foam produced by this sample.
To improve accuracy, repeat this test with fresh reagents.
5. Record your data in the following table.
| Sample |
Treatment |
mm of foam |
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6. To the second tube, add 1g of liver. Record
your data!
7. Based on the equation in the introduction, what two
chemicals are being produced? What do you think the bubbles are made of?
8. Ask your teacher to do the glowing splint test for
oxygen. Describe the results.
Catalytic Converter-- part two
Design an experiment that uses the scientific method to
test how well enzymes work a range of five different temperatures, from very
cold to body temperature, to very hot. To improve the accuracy of your
results, be sure to collect several pieces of data for each test.
The steps of the scientific method include: Stating the
problem, Forming an hypothesis, collecting and analysing data,
forming conclusions, repeating the experiment, and clearly communicating the
results to others, so that they can understand, and if necessary, repeat your
work. Your experiment will be judged on how well it uses the
scientific method. Be sure to include everything you did in a
logical sequence so that others could repeat your work.
You will be graded using the following rubric:
Did you state the problem clearly
5 points
Did you include a testable hypothesis?
10 points
Are all the materials you used listed?
10 points
Is your procedure complete and logical?
25 points
Are your results described in a paragraph?
20 points
Did you collect more than one piece of data
for each temperature you tested?
5 points
Did you organize your data into a table?
5 points
Did you neatly graph your results?
10 points
Do your conclusions explain your results,
and relate them to real life?
10 points
Primary, Secondary, and Tertiary
Protein Structure
Primary structure-amino acids are
linked into a particular sequence 
Updated: April 01, 2008
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