DNA Extraction Summary
What is DNA? What does it look like? In this activity, students extract DNA from strawberries using diluted dish soap
alcohol. The long tangled DNA strands that ultimately form may be collected using a bamboo skewer or glass stirring
. ,.
Objectives
•
•
•
•
Extract DNA.
Recognize that DNA is found in all cells.
Explain the steps needed to isolate DNA from a cell.
Begin to describe the structure ofDNA-that it is a long, invisibly thin polymer.
Vocabulary
•
•
•
•
DNA
Nucleus
Cell
Membrane
Materials Each set of partners needs: • 1 fresh strawberry (frozen strawberries also
work fme although they are not nearly as much
fun to eat)
• 1 plastic bag
• 1 150 ml beaker
• 1 clear glass or plastic test tube
Extraction buffer recipe:
• 450 ml distilled water
•. 109 table salt
, 50 ml Dawn dishwashing detergent
For the whole class to share:
• 90% ice cold rubbing alcohol or ethanol
• eye droppers for dispensing solutions
• 1 paper towel
• 10 ml extraction buffer (see recipe below)
• 1 bamboo skewer or glass stirring rod (DNA
tends to stick more fiercely to bamboo than
wood - however, bamboo is MUCH cheaper)
Teacher Background
Strawberries are used in this activity because they are octaploid, meaning they have 8 copies of every gene rather than the
usual 2; thus providing prodigious quantities of DNA to extract. Naturally, strawberries are also relatively inexpensive and readily
available. Other sources of DNA to experiment with include kiwis, bananas, and calf thymus.
The DNA molecule is an invisibly thin, very long strand. The DNA found in each human cell is almost 2 meters long. If the
entire DNA in a human adult (that's 100 trillion cells) were laid end to end, the DNA would stretch 113 billion miles. That would take
you to the sun and back 610 times. Even though DNA is invisible to the naked eye, no microscopes are needed! The reason is that you
release so many DNA strands that they tangle together into a thick cable, visible without magnification. For example, it would be the
same as ifyou took a thin piece of thread and held it up on the far end of the hallway. You probably wouldn't be able to see the thread
from that distance. However, ifyou took the thread and tangled it up with a hundred thousand other threads, you would be able to see
the tangled clump from far away because there is so much of it.
The process itself is fairly straightforward. First the cell walls are broken open by smashing the strawberries in a plastic bag.
Next, detergent is used to dissolve the cel~ and nuclear membranes. The membranes are made of lipids (fat) and the detergent will cut
through the membrane just like it cuts through grease on a dirty plate when washing dishes. Some salt is present in the detergent
solution in order to match the osmolarity of the cells.
Now you have a big mixture of smashed cell walls, dissolved membranes, loose DNA and random other cell parts. This
mixture is filtered through paper towels. Finally, you take advantage of the fact that DNA is soluble in water but not in alcohol. In
fact, alcohol makes DNA clump together. Thus a layer of alcohol laid on top of the filtrate. Any DNA that contacts the alcohol will
clump together, pulling the rest of the DNA strand along behind it. Soon you should see gossamer white strands of DNA bubbling
their way up from the red strawberry extract. The DNA may be collected by twirling a bamboo skewer or glass stirring rod in the
::., ·tion. The DNA will spool itself around the skewer and can be pulled out of fue solution.
Adapted from: A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org)
PRE-ASSESSMENT­
. Some cell biology experience (enough to know that DNA is located in the nucleus of a cell and that membranes are made of lipids) is
useful. If students are not aware ofthese facts, expect to spend at least 10 minutes longer teaching these ideas before starting the
extraction.
Getting Ready:
1..Purchase strawberries. 2.. Prepare the extraction buffer.
4. Wash the strawbemesand rernovethe green
tops. Set out theteIna.irider ofthe materla1s.
d
, 3.~Put the alcohol in the freezer pron.ice.
·ENGAGE­
1. Have students write down a few sentences to describe what DNA is and what they think DNA looks like. After this lab or the
series ofDNA modeling activities, they will come back to this naive description to revise their answers with a more .scientific
one.
2. Draw a diagram on the board showing DNA (as a long tangled thread) within the nucleus of a cell. Label the DNA, nucleus,
cell membrane, and cell wall. Remind (or teach) students about basic cell structure.
3. Tell students that they will be extracting the DNA from a strawberry and will then be able to look at the DNA. Briefly
describe the process explaining the purpose of each ofthe steps.
EXPLOREIEXPLAIN­
4. Pass out plastic bags and strawberries. Students should put the strawberry in the bag, squeeze out most ofthe air and seal the
bag. The strawberry can then be crushed into juice and pulp. Try to squish all ofthe chunks into an even, smooth puree. Warn
students not to pound the strawberry on the table or risk the bag bursting and getting strawberry pulp all over themselves and
the classroom.
5. Next, open the bag and add ,,1 0 ml of extraction buffer (approximately 10 eyedroppers full). Seal the bag again and gently mix
the strawberry juice with the extraction buffer. Warn students not to mix too vigorously or it will generate a lot of bubbles
and can't be fIltered effectively. Use a gentle tilting back and forth motion while lightly squeezing the bag.
6. Set up a fIltration system. I had students wrap a paper towel around their fmger then put their paper-wrapped finger into the
mouth ofthe beaker. When you remove your fmger, the paper towel should form a well into which the strawberry juice can
be poured.
7. Carefully pour the extract into the well in the paper towel. Allow the juice to fIlter through the towel into the container below.
Let it drip for 3-5 minutes. Do not squeeze the towel or you will create lots of bubbles, disrupting the interface needed in the
next step.
8. Carefully transfer liquid from the beaker into the clear test tube until the test tube is about a third full.
9. Slowly add 3 ml (3 eye droppers full) of ice cold alcohol to the test tube. The alcohol should be added so that it trickles down
the side of the tube before pooling on top of the strawberry extract. You should end up with a red bottom layer and a clear top
layer.
10. Have the students make observations of anything going on in the clear alcohol layer. You may wish to have students write
down observations at this point.
11. After 2-3 minutes, a skewer or stirring rod can be inserted into the tube and gently swirled around. This will spool the DNA
around the stick. The DNA can be pulled out of the tube and stored in a tube filled with some alcohoL Students may safely
touch the DNA although the DNA should NOT be tasted under any circumstances.
12. Have st udents clean up their areas.
EVALUATION- Have students answer summary questions about the extraction
a. b. c. d. e. Why is it necessary to mash the strawberries?
g. Can you see a single strand of DNA without a
What is the purpose of the detergent?
microscope? Explain how you were able to see
What is the purpose ofthe salt?
the DNA in this experiment without
Name a liquid that DNA is not soluble in.
magnification.
Is the DNA that you extracted pure? What else
h. Is DNA found in all living or once living cells?
1.
might be attached to the DNA?
Since the strawberries were once living, and we
f. Why might some people get more DNA than
extracted DNA from them, what does this mean
others?
about the foods you eat?
EXTENSION­
1. Make models of DNA (see DNA Models lesson).
2. Try to isolate DNA from other soft fruits and vegetables. This may even be done as homework. Compare the
DNA yields and discuss why different plants would give different results.
RESOURCES­
• UCSF's Science and Health Education Partnership (http://biochemistry.ucsf.edul~sep/).
• Carolina Biological (http://www.carolina.com).
Adapted from: A MyScienceBox Lesson Plan by Irene Salter (http://www.mysciencebox.org)
CANDY DNA REPLICATION LAB Objective: Describe the basic process of DNA replication and how it relates to the transmission and
)ervation of the genetic inforlnation.
Matenals:
Twizzlefs chunks (red and black) - 24 piece each color
Gum drops or coloted marshmallows (4 different colors) - 6 of each color
Wooden toothpick halves - about 70
Note: Be sure that working surfaces and hands have been cleaned before starting this activity, if you intend to consume your models after
finiShing.
Procedure:
1. Gather the supplies you need. The red licorice represent the phosphate backbone with the part of the
gummy representing the deoxyribose sugar. The gumdrops will represent the different nitrogen bases.
Choose any order you want, but remember to follow the base- pairing rule
2. Assign one nitrogen base to each of the four colors of gum drops or marshmallows. Adenine (A) =_ _ _ _ _ __ Thymine (T) = _ _ _ _ _ __ Cytosine (C) Guanine (G) =_ _ _ _ _ __ 3. What do the black Twizzlers represent?_ _ _ _ _ _ _ _ _ _ _ __
What do the red Twizzlers represent?_ _ _ _ _ _ _ _ _ _ _ __
L What structure is formed from a red Twizzler, a black Twizzler and a gum drop (or marshmallow)?
5. Prepare six individual nucleotides: use toothpicks to connect one black to one red Twizzler piece. Then
add one color candy piece perpendicularly to the black candy. Is this a full DNA strand? Explain why or
~~
:
6. Assemble nucleotides into a polynucleotide strand by connecting the red piece of one nucleotide to the
black of another. Continue until a strand of six nucleotides has been constructed. You may want to use
the diagram we went over last class as a' guide. DRAW THIS IN YOUR JOURNAL
7. Which combinations of two bases form the complimentary base pair "rungs" ofDNA?
8. Assemble a strand that is complementary to the strand that you have already built. Place the second
strand next to the first so that the complimentary "bases" touch. DRAW TIDS STRUCTURE IN
YOUR JOURNAL
9. Have your teacher check your model and initial your journal _ _ _ _ _ _ _ _ _ _ You are now
ready to REPLICATE!!!!
10. To demonstrate replication, first make 12 more nucleotides with the same nitrogen bases as the fIrst two.
strands. "Unzip" the DNA double strand one "rung" at a time. Assemble th~ proper nucleotides, one by
one.DRAW TBlSNFJW S'tRUCTURE ALONG WITH THE "OLD" ONE
.
. 12. After you demonstrate this to the· teacher you may dispose of yourmodeis. This is one case where· you·
may eat yOlJr sCierice pr()ject; if youhave kept everything clean. Be sure to remove toothpiCks be/oreyou
eat!!!
.
13. Clean up, being sure that no toothpicks or sticky residue is left behind. Wash your hands!
14. Conclusion Questions:
What is the function of DNA?
Why is it so important that the order ofbase pairs stays the same?
What would happen ifthere was a change in the base pair sequence?
What special proteins make replication of DNA possible?
What is the difference between replication and duplication?
At which stage of cell division (mitosis) does replication take place?
PROTEIN SYNTHESIS MAKES SENSE! Purpose: To help students understand the role of DNA, mRNA, tRNA, and amino acids in the process of protein "-Vllthesis. This activity can also be used to introduce the concept of mutations. . Introduction: Students will use the steps oftranscription and trarislati()fl to assemble a protein that formsa sentence ..
. Members of groups will use the handout to workthrough each step oftlIeprocess. Group sizesof26r 3 workbest. .
Nucleus: A table (or the floor) in the middle of the room which holds the DNA code cards.
1. There are 20 different single strands ofDNA. Take a moment and code for the complementary strand of the
DNA you have.* (Lower proficiency students can use the one that has the complementary strand already on it.)
The bold stand represents the template strand and is the one that will be used during transcription. None of the
DNA cards can leave the nucleus. Students will try to take them to their desks; emphasize why they must
transcribe them in the nucleus.
2. The first step is unzipping (un-Velcro) the double strand of DNA.
3. They must copy the bold DNA template onto the top strand in the nucleus on their handout. This strand should be
labeled "Template DNA".
4. The students must transcribe the RNA code from the template stand ofDNA onto the bottom strand in the nucleus
on their handout. This strand should be labeled "mRNA" and the process should be labeled "Transcription." This
entire process should be done while in the area of the nucleus, because DNA cannot leave the nucleus.
5. Tell them to record the number that is on the DNA card-it makes checking for accuracy easier later. Ribosome: 1. The student desks or tables are the ribosomes; this is where they will decode the mRNA codons to know which
tRNA they need to [md the correct amino acids (words).
2. The mRNA molecule should be copied onto the ribosome at the bottom ofthe handout.
3. The dotted arrow represents the mRNA molecule leaving the nucleus and combining with a ribosome.
4. Using the mRNA, they determine the correct anticodon for each on the tRNA's above the strand . .t'RNA: 1. After they have identified the tRNA anticodons, anticodon cards are distributed around the perimeter of the room.
Each anticodon card has a word on the back.
2. When assembled in the correct order the sentence will read: "Start-sentence (some silly)-Stop."
3. If the anticodon cards are clustered with all those beginning with the same letter in the same part of the room,
students can find the cards quicker.
Report Your Protein:
L Student groups will read their sentence to the teacher. (It is easiest for you to check if they tell you the number of
the DNA card.)
2. If it is not correct, they have to go back and begin again to determine when their mutation occurred.
WATCH OUT FOR MUTATIONS!!! If students incorrectly transcribe the DNA or mRNA, then a mutation will occur and the sentence will not make sense or not be complete. Materials:
• 20 DNA template cards
• 64 Anticodon cards
• Students need diagram worksheet and pencil Teacher Preparation: • Print the DNA strands on cardstock. Cut the double strand into two pieces. Cut close to the template DNA and
leave room above the complementary strand ofDNA as shown by the dotted line on DNA strand 1.
• Once you have laminated the cards, place pieces of Velcro on the extra space on the complementary strand.
Position the other side of the Velcro on the template strand so that the nitrogen bases of the two strands lay right
next to each other.
• Make tRNA cards with words on back. Make sure the right words on are the back of each anticodon card. They
are made to be run front and back.
• Prepare copies on the handout.
DNA template cards:*
-T
. .·-A-.
. C. -AAA~
. -.. G-.....t-.·.T-.-A.·'-G.·.-A-G
.~A-G-T-A. ·G.-:. .:. . ,I . ,-'-11••...-r.-A. •. C-·,.,•.-.~-c-r:-c.• --'cC-G"'-A-G-A-G----'-G-A----'.· ~.
. ~:r.~ I . .
..... ..'
.'.
. GGCAG.A:GGY.AT:c;
.. lkr--!
.•
.
TAC ACACACAGG GAC CTTAATC ~.
TAC AGG TAA ACG GCG I
CAAATC I
.
~ci~~ruGAC ATT·AGAI
r.
TACAATGTGCAGTGcl
CTATC I 14. TACTAAAGGGAAATG
TAT TCAATC [
TAC ATA CTT CCG AGA I . GCATC I
.
TAC CCA ACC GGT AGG
GAAGCATC
6. TAC CCC CCG AGA AGC CCTATC
15. TACTAA TCCTCGTCT
CGGCGT ATC
16. TACATAGATCTGCTT
CCG AGA AGC ATC :
[17. TACCCCCCGGAATGAI
rrGCATC I
[
TAC CGA CGC CGG CGT I
_Tci Is.
18. TAC TGG GTA TGT CGG !CGTATC
TAC CTA CTC ATA GAT CTGI
.CTTATC I
19. TAC TTA CCG AGA TTC
TTGTTT ATC
[
TAC AAG CAG GTC CAT I
TC I
o. TAC TTA TCC TCG TGG
GTTT ATC
10. TAC CCC CCG GCA GCC GCGATC. Anticodons and the words to write on the back of each one:
AUC=STOP
AUG=START
CCG=IS
CGC=WATER
UAC=START
CCU=
SUBJECT
CGG = EVERY
AAA=WHO
CGA=DRINK
CGU=DAY
AAC=FROM
AAG=
MUTATIONS
AAU=SAD
ACG=
HAVING
ACC=CHIP
ACU=CRY
ACA=
DESIGNER
AGA=THE
AGG=ARE
AGU=
BEATLES
AGC-BEST
AUA=ROCK
UAG=OUT
AUU==UP
CAA==YET
CAC==JEANS
GENES
CAG = MAKE
CAU == TRAITS
CCA=
CHOCOLATE
CCC=
BIOLOGY
CUA=I
CUC-LOVE
CUG=ROLL
CUU = MUSIC
GAA-ALL
GAC=MADE
GAG = DOGS
GAU=AND
GCA=SO
GCC=MUCH
GCG=FUN
GCU
EDUCATION
GGA=DOOR
GGC=TO
GGG­
FUTURE
GGU==
COOKIES
GUA=A
GUC==NEW
GUG=
MOVIES
GUU == LET
UAA=WE
AUG==IN
UAU==THIS
UCA==
TOGETHER
UCC=MUST
UCG=BE
UCU==
INFORMED
UGA=
AROUND
UGC=ME
UGG-READ
UGU=LITTLE
UUA=DNA
VUC CODE
UUG=FOR
uuu = LIFE
20 Sentences (Answer Key):
"
I.
Who let th¢ dogs out?
2.
Designer jeans genes are made from DNA.
3.
Are we having fun yet?
4.
Rock music is the best.
5.
Chocolate chip cookies are the best!
6.
Biology is the best subject.
7.
Drink water every day.
8.
I love rock and roll music.
9.
Mutations make new traits.
,~
10. Biology is so much fun.
II. Education is the door to the future.
12. Who made up the code?
13. Sad movies make me cry.
14. We are all in this together!
15. We must be informed every day.
16. Rock and roll music is the best!
17. Biology is all around me.
18. Read a little every day.
19. DNA is the code of life.
/
20. DNA must be read for life.
EVALUATION:
.' •
•
Determine if students produce the right sentence for their sequence of DNA. Ifthey do, students have correctly transcribed
the DNA into mRNA and translated the mRNA usingtRNA.
Use the protein synthesis sequencing strips to assess student{;. after the activity. Distribute a set of strips to each student and
allow theniio put them in the corieetorder. The cotrect sequ.ence is:
1. RNA polymerase unzips the DNA~
2. RNA free nucleotides in the nucleus bond to the template strand of the DNA, forming mRNA.
3. mRNA leaves the nucleus and goes into the cytoplasm..
4. One mRNA codon enters the ribosome.
5. A tRNA picks up an amino acid.
6. The tRNA brings the amino acid to the ribosome, matching the anticodon to codon.
7. The tRNA drops offthe amino acid and tRNA and mRNA leave the ribosome.
8. Amino acids stack up (attached by a peptide bond) until a stop codon is reached.
9. A polypeptide is formed.
10. The polypeptide folds.
11. The polypeptide combines with other polypeptides to make hemoglobin.
12. The hemoglobin is faulty because of an incorrect amino acid. Results in sickle cell anemia.
Print these out, cut them into strips, and place them in plastic bags for the activity. Have the students do
them in groups.
RNA polymerase unzips the DNA.
:,
/'
,
RNA freettucleotides in the nUcleus bond to the template strand ofthe DNA, forming :m.RNA.
mRNA leaves the nucleus and goes into the cytoplasm.
One mRNA codon enters the ribosome.
A tRNA picks up an amino acid.
The tRNA brings the amino acid to the ribosome, matching the anticodon to codon.
The tRNA drops off the amino acid and tRNA and mRNA leave the ribosome.
Amino acids stack up (attached by a peptide bond) until a stop codon is reached.
A polypeptide is formed.
The polypeptide folds.
The polypeptide combines with other polypeptides to make hemoglobin.
The hemoglobin is faulty because of an incorrect amino acid. Results in sickle cellI anemia.
7
1. TAC AAA GTT AGA GAG TAG ATC
GTTT
.A,..A,4l.""
reT C
ATe TAG
2. TAC ACA CAC AGG GAC AAC TTA ATC TGT GTG CC CT TTG
T
3. TACAGG TAAACG GCG CAAATC G C
Al~T
Tee
4. TACATACTTCCGAGAAGCATC G
5. TAC CCA ACC GGT AGG AGA AGC ATC c
6. TAC CC.CCCG A.GAAGCCCTATC
GGG GGC TCT TCG GGA TAG
7. TAC CGA CGC CGG CGT ATC
G GeT
Gce GCA TAG
8. TAC CTA CTC ATA GAT CTG CTT ATC GAC GA TAG 9. TAC AAG CAG GTC CAT ATC C
G
10. TAC CCC CCG GCA GCC GCG ATC _1. TAC GCT CCG AGA GGA GGC AGA GGG ATC ATG GA GGC TCT CCT CCG TCT
C TAG
12. TACAAAGACATT AGATTCATC
A1'G TTT
G TAA TeT LL\AG T G
13. TAC AAT GTG CAG TGC ACT ATC·
14. TAC TAAAGG GAAATG TAT TCAATC T
T
15. TAC TAA TCC TCG TCT CGG CGT ATC 1~.
TACATA GATCTGCTTCCGAGAAGCATC G TAT eTA GAC GAA GeTeT TCG TAG
17. TAC CCC CCG GAA TGA TGC ATC
ACG
GGG GC TT
18. TAC TGG GTA TGT CGG CGT ATC
GC GCA
A
19. TAC TTA CCG AGA TTC TTG TTT ATC G
err
G
.4. A ........
20. TAC TTA Tee TCG TGG TTG TTT ATC PROTEIN SYNTHESIS MAKES SENSE!
(Follow the process ofProtein Synthesis from beginning to end)
o
o
TemDlate DNA
00
. mRNA
o
tructions: {S pts each}
Label all parts of the cell
you see here using your
own arrows and labels
Follow the process of
transcription and write
the DNA strand and its
mRNA complement
Follow the process of
translation and write the
o
o
complementary code on
thr
I)some
COII'r'lete the protein
synthesis process by
writing the amino acid
sequence (protein)
Protein Sentence: Answer
o
o
Building Monomers of Macromolecules Introduction:
The term macromolecule by defmition implies "large molecule". In the context of biochemistry,
tue tetm may.be applie<itothe four large molecules" that makeup organistlls ...... nucleotides, proteins,
.
carbohydrates, and lipids.. MacromoleculeS-are made of smaller subunits called monomerS. Monomersare·
composed offour elements that make upalUiving things; Carbon, Hydrogen, Oxygen, and Nitrogen.
In this lesson, students fonn the structure of the macromolecules using foods. Students use vegetable ~lices
or fruit to create models from drawings. Common vegetables represent elements found in the
macromolecules and spaghetti or toothpicks are used to represent the bonds between the molecules.
Students will recognize the way macromolecules are put together and discover how smaller molecules are
repeated to fonn polymers.
Ohjective:
lents will construct the basic components of organic molecular structure.
Materials:
Use different household or food items to represent the different elements Example: Blueberries= Hydrogen Red Grapes= Oxygen Green grapes= Carbon Radish= Nitrogen Bonds= wooden toothpicks or dry spaghetti pieces Task: Construct each of the following monomers and answer the questions. After constructing each monomer, bring your lab sheet & model to the teacher to be approved. REMEMBER:
1. Molecules are 3-dimensional so models will NOT BE FLAT!
2. When constructing a functional group (-OH, -COOH, -NH2) PUT BONDS BETWEEN ALL
ELEMENTS!!
3. Create a key in your journal identifYing which food represents which element. Refer to this in
building your models.
4. Draw all the molecules you create into your journal and answer the corresponding questions for
each completely.
Construct glucose. .Correctly NUMBER the carbons on this picture in your journal. Ii
H--
~-
OH
I
C
/~
0
HO-C-H \~ .
\
H-C-OH
7/
c-----c
i
H
I
0
H
1. What is the chemical formula for glucose?
2. Glucose is a monomer for what macromolecule?
3. What other simple sugar(s) has the same chemical formula as glucose?
4. Simple sugars like glucose are called
.M.... _ _ _ _ _ _ _ _
5. What is the function of carbohydrates for the body?
/'
,
Construct Glycine. Place a BOX around the amino group and the carboxyl group on this picture in your
.
journal.
H
\
H
I
0
II
N-C-C
/
I
\
H H O-H
6. Glycine is what type of monomer? (Two words)
7. Name the 4 things attached to the center carbon in ALL amino acids.
A.
B.
c.
D.
8. How many amino acids exist? (Look in your book or research on the Internet)
9. What element is found in amino acid that isn't found in simple sugars like glucose or fructose?
10. Amino acids join together to make what type of macromolecule?
11. What are some of the functions of proteins in the body? (List several)
3
Construct· Glycerol. . . ·.Fl*c~~~mC~E.~t6lln4i;:tJlYdtoXYI;3toUP un your drawiijg iny(uirjou~Ila:I. .
_\
I
-C-C-'C­
I
I
I
I
I
000
I
:r::
I
:r:
I
:t:
Glycerol
12. Glycerol is one of two molecules that make up a monomer known as
..L _.___._. __._____________ L'
13. Besides glycerol, what 3 other molecules make up a triglyceride?
14. Glycerol and other organic compounds with an -01 ending are called
15. Triglycerides are the monomers for what type of macromolecule?
16. Give 3 types of lipids and give their function.
A.
B.
c.
.
Construct a Fatty acid. Place a BOX around the hydrocarbon chain on your pictures in your
journal. Circle the carboxyl group on. both pictures in your journal.
Saturated Unsaturated Fatty acids are made of long chains of_ _ _ _ _ _ atoms with attached
- - - - - - atoms.
18. How many bond(s) does each carbon atom have?
19. How many bond(s) does each hydrogen have?
20. What 3 elements make up fatty acids?
A.
B.
c.
5
Construct Cytosine. 21. Cytosine is an example of a nitrogen base found on _ _ _ _ _ _ acids.
22. Name the nucleic acids found in all organisms.
23. List the name for the elements making up cytosine.
24. Name the other 3 nitrogen bases found on DNA.
. 25. What nitrogen base is found on RNA but not DNA?
6
STUDENT WORK SHEET: THE MONOMERS OF MACROMOLECULES All key components of every living cell are made of macromolecules. The four kinds of macromolecules
~-~~ lipids, carbohydrates, nucleic acids, and proteins. Most macromolecules are polymers constructed of
ly organic molecules called monomers.
These molecules represent one level of basic building blocks oflife. These monomers, or single molecules, can
be joined with other monomers to form larger units (polymers). They can be divided into four groups:
1. carbohydrates (sugars for-energy and structure)
2. lipids (fats for membranes and energy storage)
3. nucleic acids (information bearers)
A. proteins (the molecular machines of the cells).
Try to determine some ways of classifying these molecules below into four groups. There may be more than
one right answer. Number each molecule 1.2,3 or 4.
-~-
P'-aIly, what different kinds of atoms are present in these molecules? Write the initials of each kind of atom
.
>• . " " - - - - - - - ­
Factors Affecting Enzyme Activity
Introduction
.·-l-lydrogen peroxide (EIz02) is a poisonous byproduct of metabolism that can damage cells if it is not removed.
atalase is an enzyme that speeds up the breakdown of hydrogenperoxide into water (lIzO) and o:xygen gas
(02),
2H20 2 forms 2H20 + 02
REMEMBER: A CATALYST is a substance that lowers the activation energy required for a chemical
reaction, and therefore increases the rate of the reaction without being used up in the process. Catalase is
an enzyme, a biological catalyst, for which hydrogen peroxide is the substrate.
The assay system used in this lab consists of a small filter paper disc which is coated with the enzyme
and then placed into a beaker of substrate (hydrogen peroxide). As the catalyst breaks down the hydrogen
peroxide into water and oxygen gas, the bubbles of oxygen collect underneath the filter and make it rise to the
surface ofthe hydrogen peroxide. The time it takes for the filter to rise is an indication ofthe rate of enzyme
activity.
Rate of enzyme activity distance (depth ofhydrogen peroxide in mru)/time (in sec). We will assume
that each filter is coated with the same amount of catalase (except in the investigation of the effect of enzyme
concentration on enzyme activity).
The enzyme has been prepared for you as follows: 50g of peeled potato was mixed with 50 ml cold
distilled water and crushed ice and homogenized in a blender for 30 seconds. This extract was filtered through
cheesecloth and cold distilled water was added to a total volume of 100 mI. Extract concentration is arbitrarily
set at 100 units/mI. ENZYME SHOULD BE KEPT ON ICE AT ALL TIMES!!
Materials: catalase, hydrogen peroxide 3% and 1.0%, forceps, filter paper discs, water, ice, water baths, vials, marking '~ncils, stopwatch or timer .!ch group will investigate and report on two of the factors. Steps common to all parts of the investigation:
1. Using forceps, dip a filter paper disk (use the three hole punch to create disks of equal size) into the appropriate enzyme solution, then remove it and drain it quickly on a paper towel. Always swirl the enzyme solution before dipping the disks. 2. Place the disk into the beaker of hydrogen peroxide so that it sits on the bottom. When the disk touches the
substrate solution, begin the timer and record the time required for the disk to rise to the surface. Remove the
disk after it reaches the surface. (WHY?)
3. Perfonn 5 trials and record all your data. Calculate the average.
A. What is the effect of enzyme concentration on enzyme activity?
1. Set up five beakers containing 40 ml of3% hydrogen peroxide each. Measure and record the depth of the hydrogen peroxide in each beaker.
.
2. Dilute the enzyme as follows. Remember that the enzyme stock is 100 units/mL. Make each dilution in a separate beaker and label each: 100 units/ml = 20 ml 100 units/ml 80 units/ml 12 miiOO units/ml + 3 ml cold dH2 0 50 units/ml lO ml 100 units/ml + 10 ml cold dH2 0 20 units/ml = 3 ml 100 units/ml + 12 ml cold dH20 'nits/ml = 20 ml cold dH20
3. Test the reaction time for the enzyme solution at 100 unitslml
4. Repeat this procedure for each ofthe other enzyme dilutions
5. Perform five trials. Record your results.
·
.
B~ What is the effect ()f substratec()ncenttanon ()nen.qJ;ltcadivify?
1. Obtaina beaker of catalase at 100unitslml
.
2. Dilute the substrate (hydrogen.peroxide) as described below. Each dilution should be made ina separate,
labeled beaker. Measure and record the depth of the hydrogen peroxide.
3.0% H202: 40 ml3% H202
1.5% H202: 20 ml 3% H202 + 20 ml distilled water
0.75% H202: 10 ml 3% H202 + 30 ml distilled water
0.38% H 202: 5 m13% H 202 + 35 ml distilled water
0.0% H202 : 40 ml distilled water
3. Test the reaction time for 3% H202.
4. Repeat this procedure for each ofthe substrate dilutions.
5. Perform five trials. Record your results.
C. What is the effect of pH on enzyme activity?
1. Obtain 1 beaker of 40 ml 1% H202. Measure and record the depth of the hydrogen peroxide.
2. Label 5 small beakers as follows: pH3, pH5, pH7, pH9, pHIl and dilute catalase into the appropriate beaker
as directed below:
pH 3: 5 mL catalase + 5 mL pH 3 Buffer
pH 5: 5 mL catalase + 5 mL pH 5 Buffer
pH 7: 5 mL catalase + 5 mL pH 7 Buffer
pH 9: 5 mL catalase + 5 mL pH 9 Buffer
pH 11: 5 mL catalase + 5 mL pH 11 Buffer
3. Test the reaction time at pH 3.
4. Repeat the procedure for each pH.
5. Perform five trials. Record your results.
D. What is the effect of temperature on enzyme activity?
1. Set up an ice bath (OOC), a room temp water bath, a 37°C bath and a boiling water bath.
2. Place 5 ml of catalase at 100 unitslml in each of 4 test tubes.
3. Place 1 test tube in each ofthe water baths.
4. Place 40 mil % H202 in each of 4 beakers.
5. Measure and record the depth ofthe H202.
6. Place 1 beaker in the O°C bath and leave the other 3 beakers at room temperature. This is necessary because
heat will destroy the hydrogen peroxide.
7. Allow the catalase and substrate to incubate at each temperature for about 5 minutes, then test the reaction
time at each temperature. Be sure to place the catalase from each temperature in the hydrogen peroxide ofthe
appropriate temperature.
8. Use the second room temperature beaker of hydrogen peroxide for the boiled catalase. DO NOT BOIL
HYDROGEN PEROXIDE!
9. Time how long it takes the filter to rise at each temperature.
10. Perform five trials. Record your results.
Analysis:
For EACH variable; use the AVERAGE rates from the class data to construct a graph of the independent
mabIe vs. the dependent variable. TIlls means you will have four graphs:
·1. EnZyme concentration (x axis) vs. Rate (y axis)
2. Substrate concentration (x axis) vs. Rate (y axis)
3. pH (x axis) vs. Rate (y axis)
4. Temperature (x axis) vs. Rate (y axis)
Questions to stimulate your tiny brains:
1. What is the effect of enzyme concentration on enzyme activity? Explain how enzyme activity changes
as enzyme concentration decreases, and discuss why this occurs (on a molecular level).
2. What is the effect of substrate concentration on enzyme activity? How does enzyme activity change as
substrate concentration decreases? Explain your observations by discussing this reaction on a molecular
level.
3. How does temperature affect the activity of catalase? Explain your observations by discussing the effect
of temperature on protein structure. Discuss both high and low temperature effects.
4. How does pH affect the activity of catalase? Consider both high and low pH, and explain your observations by discussing the effect of pH on protein structure. 5. Ectothermic organisms have body temperatures that vary with the temperature of their surroundings.
Discuss the effect this variation might have on the functioning of enzymes in these organisms. Suggest
some ways ectothermic organisms might cope with this problem.
Name: __________~____________--
Date: _____________
Student Exploration: Freezing Point of Salt Water
_ : freeze, freezing point, liquid, melt, melting point, solid, transformation rate
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. In the winter, people often buy large bags of rock salt to sprinkle on their walkways. Why do
people do this? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
2. The _;ISiI~ of pure water is 0 °C (32 OF). How do you think adding salt to water
affects its freezing point? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
Gizmo Warm-up
People often use salt to alter the freezing point of water.
The Freezing Point of Salt Water Gizmo ™ shows you how
this works.
1. With the Room temp. set to 0.0 °C, observe the water
molecules in the Molecular view. Describe the motion
of water molecules in the
phase:
&1
2. Set the Room temp. to -10.0 "C and observe. What is happening?
--------------
The process of changing from a liquid to a ~~lil is called If.1~i,r~9.
3. Describe the motion of molecules in a solid:
-------------------------
Activity A:
Fr~ft;zir-g ppint
.depression
Get the Gizmo ready:
• Slick~e.~et.
. .. .
.• SettheRoomtemp.to5.0 C!C.
Question: How does salt affect the freezing point of water and the melting. point ofite?
1. observe: With the room temperature at 5.0 °C, the water should be in a liquid state. Lower
the Room temp. one degree at a time until the water first starts to freeze. Look at the
thermometer inside the container of water
A. What is the freezing point of pure water? _________________
B. Lower the Room temp. a few more degrees. What do you notice about the water
temperature as the water is freezing?
C. Lower the Room temp. to -10.0 °C, wait until all the water has frozen, and then wait
a little while more. What happens to the ice temperature after all the water is frozen?
D. Now raise the Room temp. back to 5.0 °C and observe the thermometer inside the
This is the
of ice.
container. At what temperature does the ice
lilt?
fIiIIi'fJlllil
2. Predict: How do you think adding salt will affect the freezing and melting points of water?
3. Experiment: Click the Add 50 g button to add 50 grams of salt to the water. Lower the
Room temp. to -10.0 °C and observe the temperature as the water freezes.
What is the freezing point of this salt solution? _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
4. Observe: Look for the salt particles in the ice. What do you notice? _ _ _ _ _ _ _ __
(Activity A continued on next page)
Activity A (continued from previous page)
5. Experiment: Afterthewater has completely frozen, raise the Room temp. to 5.0 °C.
Otiseniethe water temperature as the ice melts.
What is the melting point of this salt solution? ____________________
6. Collect data: Use the data you have collected so far to fill in the first two rows of the table
-below. Then, find the freezing and melting points of water with 100 grams of salt.
Amount of salt (g)
Freezing point (OC)
Melting point (OC)
Og
50 g
100 g
7. Summarize: How does increasing the concentration of salt affect the freezing and melting
points of water? _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __
8. Analyze: How much is the freezing point lowered by adding 50 g of salt? _ _ _ _ _ __
9. Test: Based on your data, what do you expect the freezing and melting points to be when
150 grams of salt are added? How about with 200 grams of salt? Write your predictions in
the appropriate columns below.
Amount of salt
Freezing Point
(predicted)
Freezing Point
(actual)
Melting point
(predicted)
Melting Point
(actual)
150 g
200 g
After writing your predictions, use the Gizmo to find the actual values. Fill in as much of the
table as you can. (Write "less than -10°C" or "< -10°C" if the actual value is less than the
minimum room temperature available in the Gizmo.)
1O. Think and discuss: Why do people add salt to roads and walkways in the winter?
Activity B:
Get the Gizmo ready:
• ClickReset.
t~ITIo~th~ Tr!:anc~'fnrrn,i:itiAn'
•
Introduction: The
is the speed at which particles are changing from one
phase to another. In thensformation rate display, the purple bar represents the speed of
liquid water changing to ice, while the green bar indicates the speed of ice changing to liquid.
Question: How does salt affect transformation rates?
1. Observe: Move the Room temp. slider back and forth, and observe the effect on the
transformation rates. What do you observe?
2. Explain: As the temperature of a liquid increases, the average speed of the molecules
increases as well. How does this account for the observed changes in transformation rates?
3. Predict: How will adding salt affect the water-to-ice and ice-to-water transformation rates?
4. Experiment: Set the Room temp. to -5.0 °C, and observe the transformation rates. Add 50 g
of salt before the ice reaches the bottom of the funnel.
A. How does adding salt affect each transformation rate? _ _ _ _ _ _ _ _ _ __
B. Now add 50 more grams of salt. What happens now? _ _ _ _ _ _ _ _ _ __