Download Model 02 - Antibiotics

Biology 100 – Winter 2013
North Seattle Community College
NAME: _____________________________
Evidence-Based Model 02 – How do antibiotics work?
This model will be a bit different from our first model. For this model we’ll have ideas of how physical things,
like antibiotic molecules and bacterial cells, might look and act, compared with our first model that was
represented largely by mathematical expressions of how our population of infected individuals changed over
time.
Scientists use explanatory models in order to be able to connect a series of ideas to explain how a natural
phenomenon might work. Their explanation includes the available evidence and existing scientific knowledge
up to that time. A model can then be tested and revised, if necessary, as new information is gained.
In this model you will concentrate on telling a story of how an antibiotic might work on a typical prokaryotic
bacterial cell inside of a eukaryotic animal. A story flows from a beginning, a middle, and an end. This story
will be mostly a picture book story supported by words when necessary to help explain your point. The
objective of this exercise is to help you to learn the cellular structures and their functions inside of two different
types of cells found in living organisms.
This type of story is called an explanatory model, where you explain how you think a natural phenomenon
works through an evidence-based explanation (or story). Your evidence, in this instance, is the information
from your observations, measurements, and reliable resources from class, your labs, and your text.
OK, so let’s get started! Here is a checklist of the following terms and concepts that you should include in your
story of how antibiotics might work.
Checklist for Explanatory Model of How Antibiotics Might Work
(Abbreviations: P = Paragraph; F = Figure; T = Table)
First, there was an infection….
P1: Give your reader a context to your story. Where is your story taking place? How did the infection get
started? Make sure you highlight that bacteria are causing the infection.
P2: Explain what Cell Theory and the Theory of Biogenesis says.
F1: Draw a picture of a typical prokaryotic bacterial cell next to a typical eukaryotic animal cell (After all, this
infection is taking place inside of an animal!)
Be sure to include AND label the following where appropriate:
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Cell membrane
Cell wall
Chromosomal DNA
Ribosomes
Cytoplasm
Nucleus
Rough Endoplasmic Reticulum
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Smooth Endoplasmic Reticulum
Golgi Apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Flagella
F2A: Draw a picture of a Gram + and a Gram – bacterial cell wall and cell membrane.
Be sure to include AND label the following where appropriate:
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Outside of the cell
Outer membrane layer of the cell wall with integral membrane transport proteins (porins)
Peptidoglycan layer of the cell wall
Cell membrane with integral membrane transport proteins
Inside of the cell
F2B: On these pictures of Gram + and Gram – bacterial cell walls and cell membranes, draw AND label
arrows to indicate the following transport processes and provide written explanations of how these processes
work:
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Simple diffusion
Osmosis
Facilitated diffusion
Active transport
F3: Explain how a cell grows by drawing a flow diagram. Remember in our flow diagrams that arrows ()
mean, “causes this to happen or go forward” and stop arrows (---| ) mean “inhibits this.”
Be sure to use the following terms:
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Building blocks
Enzymes
Macromolecules
Cellular structures
Functions of those cellular structures
Cell Growth
Underneath that flow diagram OR on separate pieces of paper, now give some examples of three different
metabolic reactions that might be happening in these cells by drawing a picture and using words to help you
explain what is going on. Be sure to include AND label the following:
 F4: Cell wall
synthesis in a
prokaryotic cell
 F5: Protein
synthesis in both
types of cells
 Peptidoglycan
 Enzymes
 Peptidoglycan cross
links
 Cell wall
 Rigid structure to
protect against
osmosis
 Bacterial cell growth
 Transcription (DNA
 mRNA by RNA
polymerase)
 Translation (mRNA
 proteins by
ribosomes)
 Proteins
 Many different
cellular structures
 Structure and work
of the cell
 Cell growth
Then, there was an antibiotic…
 F6: DNA
replication in both
types of cells
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Nucleotides
DNA polymerase
DNA
Chromosomes
Storage of genetic
information
 Cell growth
F7: Explain how a typical antibiotic works by drawing a flow diagram. Remember in our flow diagrams
that arrows () mean, “causes this to happen or go forward” and stop arrows (---| ) mean “inhibits this.”
Be sure to use the following terms:
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Antibiotic
Transport
Building blocks
Enzyme
Macromolecules
Cellular Structures
Functions of those cellular structures are missing
Inhibition of Cell Growth
OK, that was our skeleton model. Now let’s flesh out that model with some more detail.
T1: Include a table that summarizes the class lab results from our antibiotics lab. Be sure to include:
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All 3 bacteria tested, names in italics, genus capitalized, species lower case
Whether each bacterium is Gram + or Gram –
All antibiotics tested
Whether the bacterial strain was S (susceptible), I (intermediate), or R (resistant) to the antibiotic
P3: For penicillin, referring to your skeleton model of how an antibiotic works,
A: explain how it works on Gram + bacteria,
B: explain why it does NOT work on Gram – bacteria.
Be sure to include the following:
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Penicillin
Simple diffusion
Peptidoglycan
Enzymes
Peptidoglycan cross links
Weakened cell wall
Osmosis
Cell lysis
Gram- outer membrane
Refer to specific evidence from our antibiotics lab in your discussion
P4: For streptomycin, referring to your skeleton model of how an antibiotic works,
A: explain how it works on Gram + and Gram – bacteria,
Be sure to include the following:
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Streptomycin
Facilitated diffusion
Ribosomes
Protein synthesis
No protein for building cellular structures and doing work of the cell
Cell death
Refer to specific evidence from our antibiotics lab in your discussion
P5: For the sulfa drugs (SXT), referring to your skeleton model of how an antibiotic works,
A: explain how it works on some Gram + and Gram – bacteria,
B: explain how it does not work on some bacteria
Be sure to include the following:
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Sulfa drug
Facilitated diffusion
Enzyme
Folic acid synthesis
No DNA synthesis
Cell death
Active transport of sulfa drug out of the cell
Refer to specific evidence from our antibiotics lab in your discussion
P6: End off with a quick discussion about why antibiotics primarily affect prokaryotic cells and not eukaryotic
cells. In addition explain how side effects from antibiotics might happen.
Be sure to include the following:
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Cell wall: prokaryotes versus eukaryotes
Ribosomes: prokaryotes versus eukaryotes
Folic acid synthesis: prokaryotes versus eukaryotes
Endosymbiotic theory
YOU ARE DONE!