View
928
Download
23
Category
Preview:
Citation preview
ANSWER KEYfor
“Take Two and Call Me in the Morning: A Case Study inCell Structure and Function”
by
Peggy Brickman, Department of Plant Biology, University of Georgia, Athens, GA
HandoutTable 1: Differences Between Organisms (complete before class)
CHARACTERISTIC Virus Bacteria Protozoa
What differences exist in
the type and shape of the
genetic material?
RNA or DNA Circular DNA DNA in linear chromosomes
What differences exist in
the structure that provides
an outer protective barrier?
Proteins with
or without
lipids
Phospholipids
with or without
cell wall
Phospholipids without cell wall
What differences exist in
reproduction?
Only
reproduces
inside other
cells
Independent
reproduction but
asexual
Independent reproduction both
sexual and asexual
What differences exist in
size?
nanometer About 1 µm size 5–100 µm
What drugs can treat
infections?
Enzyme
inhibitors
Anti-
peptidoglycans
Drugs that affect organelles only
protists have, or enzymes only
protists use (pyrimethamine) to
make folic acid which our cells
get through diet
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
1 av 6 2010-03-03 12:24
Table 2: Mechanism of Action of Antibiotics (complete in class)
Drug Name Mechanism Why It Does Not Harm
Human Cells
Prokaryotes Amoxicillin,
penicillin, and
other betalactams
Blocks enzyme that normally
creates links in peptidoglycans
No cell peptidoglycan cell
walls
Streptomycin Blocks prokaryotic ribosomes Different ribosomal proteins
Ciprofloxin
hydrochloride
Blocks bacterial gyrase enzyme
needed to counteract excessive
twisting of DNA that occurs
when circles of DNA areunwound to be copied into
DNA or RNA
No circular DNA, DNA is
linear.
Eukaryotes Pyrimethamineand sulfonamides
Interfere with enzymes used tomake the folic acid needed to
make thymine and uracil
nucleotides; without
nucleotides, the cells have
trouble making RNA or DNA.
Human cells are affected, sodoctors often co-prescribe
folinic acid that can be
converted to folic acid in
human cells without relying
on these enzymes
Antifungal
polyenes
Combine with ergosterol
(component of fungal and
some bacterial membranes) &
disrupt and break membranes.
Ergosterol not found in
human cells; we use
cholesterol
Inhibitors of beta
glucan
Interfere with enzymes used to
create the beta glucan found in
fungal cell walls
No beta glucan cell walls
Viruses Tamiflu Blocks neuraminidase enzyme
made by all influenza A strains
(cause the “flu” and avian flu);viruses are unable to remove
sticky sialic acid can’t escape
No neuraminidase enzyme
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
2 av 6 2010-03-03 12:24
Table 3: Similarities between Mitochondria and Bacteria (complete in class)
ORGANISM Circular
DNA
Size
(µm)
rDNA
sequence
Phospholipids
similarityprokaryote or
eukaryote
Ribosomes
similarityprokaryote
or eukaryote
Divide to
makeclones
Bacteria yes 1 similar yes yes yes
Mitochondria yes 1 similar yes yes yes
Clicker Questions
To view individual slides and refer to individual images, hover over or click the appropriate CQ# at
the start of the question.
CQ1: “That’s great,” Becky said. “My Mom sent me 3 different antibiotics to kill bacteria.” Given the
description of Ellie’s test results, which antibiotic will definitely NOT work:
A: Amoxicillin, Penicillin, and other β-lactams—Blocks the enzyme that normally creates links in
peptidoglycan molecules.
B: Streptomycin—Blocks prokaryotic ribosomes.
C: Ciprofloxacin hydrochloride (Cipro)—Blocks bacterial DNA gyrase enzyme needed tocounteract excessive twisting of DNA that occurs when circles of DNA are unwound to be copied
into DNA or RNA.
The correct answer is: A
CQ2: “Wait a minute!” Ann said. “The doctor said the blobs in Ellie’s blood were 1/10th the size of hercells. Could they be Coxiella?”
A: Yes
B: No
The correct answer is: B
CQ3: “Well,” Becky admitted, “there should be differences between Ellie’s cells and the little blobs
they saw. Otherwise, it might mean one of my other suspects is the cause. These are some of the
structures normally found in all cells.”
“No,” Ann answered, “one isn’t.”
Which structure is NOT found in all cells?
A: Cytoplasm
B: DNA
C: Outer phospholipid membraneD: Ribosomes
E: Membrane-bound organelles
The correct answer is: E
CQ4: Becky’s Anti-Eukaryotic Medicines:
Pyrimethamine, Sulfonamides: Interfere with enzymes used to make the folic acid needed to
make thymine and uracil nucleotides.Polyenes combine with a component of fungal and some bacterial membranes, disrupt and
break them.
One of these drugs specifically affects one of the two eukaryotic suspects. Which test of Ellie’s bloodwould help you tell which eukaryotic suspect she was infected with?
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
3 av 6 2010-03-03 12:24
A: Presence of DNA.
B: Presence of β-glucan-containing cell walls.
C: Presence of cellulose.
D: Presence of peptidoglycan cell walls.
The correct answer is: B
CQ5: Match the description with the suspect. Use your responses to Table 1 to identify the row belowthat best describes West Nile Virus [see slide].
The correct answer is: D
CQ6: Foreign DNA sequence isolated from Ellie: ACGTGGTCGTT.
Which sequence is the best match with this foreign DNA?
A: Ellie’s nucleus ATGGTCTCAATG
B: Ellie’s mitochondria TTGGTCCGTCAG
C: Coxiella bacteria TTGGTCGGTCAG
D: Toxoplasma nucleus AACGTGGTAGTT
E: Cryptococcus nucleus ATGGTGGCAATG
The correct answer is: D
CQ7: Which letter best defines the place mitochondria would take next to their closest relatives on this
family tree of living organisms [see slide]?
The correct answer is: D
Pre- and Post-Case Questions
The following pre- and post-case questions are available in a PowerPoint presentation for instructors
who wish to use them in class.
PQ1: To distinguish between prokaryotes and eukaryotes, we need to consider:
A: The specific types of lipids present in the outer plasma membrane.
B: The type of molecule used as its genetic information.C: Whether the genetic information is enclosed in a protective layer of phospholipid membrane
bilayer.
D: Whether the organism is harmful to the cell.
The correct answer is: C
Rationale: This is a factual question. It expects students to know the differences in structure between
prokaryotes and eukaryotes. The correct answer is whether or not the genetic information is enclosed
in a protective layer of phospholipids bilayer. Both prokaryotes and eukaryotes contain phospholipids
in their membrane bilayers, and both use DNA as their genetic information. Measures ability to
differentiate between prokaryotes and eukaryotes using factors such as presence of uniquestructures. The mean pre-test score was 46% and the post-test score was 79%.
PQ2: In which way are cells and viruses different in how they reproduce? Viruses:
A: Only reproduce sexually, by fusing with another virus, cells can reproduce both sexually and
asexually.
B: Make a duplicate copy of their genetic material before they can divide in two, cells can wait
until after they have divided to copy genes.C: Only reproduce after entering a host cell, cells can reproduce alone.
D: Invade a cell after they have reproduced, cells can invade other cells without reproducing
first.
The correct answer is: C
Rationale: This is a factual question. It expects students to know basic viral biology. The correct
answer is C because viruses can only reproduce after entering a host cells, some cells can only
reproduce inside other cells, but most can reproduce on their own. A is incorrect because viruses do
not undergo sexual reproduction. B is incorrect because both cells and viruses must duplicate their
genetic information before producing more of themselves. D is incorrect because viruses invade a
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
4 av 6 2010-03-03 12:24
cell and then reproduce before going on to invade more cells, and not all cells can invade other cells.
The mean pre-test score was 76% and the mean post-test score was 96%.
PQ3: An organism has the following: proteins, DNA, ribosomes, plasma membrane, and mitochondria
(among other structures.) Select the most inclusive answer for what type of organism it could be.
A: A prokaryotic cell.
B: A eukaryotic cell, but not a plant cell.
C: An animal cell, but not a protist cell.
D: Any eukaryotic cell.
E: A virus or a prokaryotic cell.
The correct answer is: D
Rationale: This is an application question. It expects students to apply their understanding of cell
structure to determine what the cell type could be. The correct answer is D – any eukaryotic cell—
because the organism has mitochondria, a membrane bound organelle not found in prokaryotes (A)or viruses (E) but is found in plants (B) and protists (C). Measures ability to differentiate between
prokaryotes, eukaryotes, and viruses using factors such as size or the presence of unique structures.
The mean pre-test score was 22% and the mean post-test score was 36%.
PQ4: You have an infection caused by a prokaryotic pathogen. Which of the following would make a
good choice for killing off the prokaryote without harming your cells?
A: A drug that prevents duplication of long strands of DNA.B: A drug that tangles up DNA circles and prevents their duplication.
C: A filtration system that rids the body of organisms under 0.5µm in size.
D: A drug that prevents phospholipids from being deposited into new cell membranes.
E: A drug that prevents mitochondria from functioning.
The correct answer is: B
Rationale: This is an application question. Students need to recognize that prokaryotes have circular
DNA whereas eukaryotes do not, and that the safe drug would be the one that only affects
prokaryotes. The correct answer is D, any eukaryotic cell because the organism has mitochondria, a
membrane bound organelle not found in prokaryotes (A) or viruses (E) but is found in plants (B) andprotists (C). Measures ability to differentiate between prokaryotes, eukaryotes, and viruses using
factors such as size or the presence of unique structures. The mean pre-test score was 22% and the
mean post-test score was 36%. Measures ability to apply knowledge of the differences between
viruses, prokaryotes and eukaryotes to understand why various treatment methods work to
specifically kill one class of organisms while remaining harmless to the human cells or other
organisms. The mean pre-test score was 17% and the post-test score was 53%.
PQ5: Which of the following would you not expect to find in a Toxoplasma cell?
A: Rough endoplasmic reticulum
B: Lysosomes
C: Plastids
D: Mitochondria
E: Golgi
The correct answer is: C
Rationale: This is an application question. Students need to understand cell components of the
organism.
Transfer Question
TQ1: The following photomicrograph shows several human cells stained as large light purple
structures with purple nuclei (stars) infected with a pathogenic organism shown as small dark purple
circles (arrowhead). These pathogens are most likely a(n):
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
5 av 6 2010-03-03 12:24
A: Eukaryote
B: Prokaryote
C: Virus
The correct answer is: B
Image credit: Diff-Quik Stain of Ehrlichia chaffeensis in DH82 cells, 1000X. Image courtesy of
Centers for Disease Control and Prevention, http://www.cdc.gov/ncidod/dvrd/ehrlichia/Laboratory
/Laboratory.htm.
Multiple-Choice Pre-Class Preparation Questions Key
1: a, i ; b, ii; c, iii
2 a;
3 a, prokaryotic cell; b, eukaryotic cell; c, eukaryotic cell; d, eukaryotic cell; e, eukaryotic cell; f,
prokaryotic cell; g, eukaryotic cell; h, both; i, both; j, both; k, both; l, eukaryotic cell; m,
prokaryotic cell; n, eukaryotic cell; o, prokaryotic cell
4: a, i; b: ii, c, iii; d, iv; e, v
5: a, i; b: ii, c, iii; d, iv; e, v
Go back to the teaching notes
Copyright © 1999–2010 by the National Center for Case Study Teaching in Science. Please see our usage guidelines, which outlineour policy concerning permissible reproduction of this work.
Answer Key for “Take Two and Call Me in the Morning” - Case Study ... http://www.sciencecases.org/lock/cell_structure_key.asp
6 av 6 2010-03-03 12:24
Recommended