In this lesson, students connect passive transport across a semi-permeable membrane to show how the antibiotic vancomycin works to kill MRSA. Students complete two simple osmosis and diffusion investigations, learn the details of passive transport, and apply their conceptual understanding to create a comic which illustrates vancomycin's mechanism of action against MRSA. Students should already be familiar with cell structure. This lesson can be used in tandem with the "Oh, MRSA Me" LEARN lesson.
How does the cell membrane help cells maintain homeostasis? How does vancomycin work to destroy MRSA bacteria?
Students compare and contrast plant, animal, and bacteria cells to determine what part of bacteria could be targeted with antibiotics without harming host cells.
Students complete an osmosis and diffusion lab investigation.
Students explain the results of their investigation and take notes over passive cell transport.
Students complete a Card Sort to sequence the steps showing how the antibiotic vancomycin works against MRSA.
Students create a cognitive comic based on the previous Card Sort and their understanding of passive transport, explaining how vancomycin disrupts homeostasis in MRSA bacteria.
Lesson Slides (attached)
Diffusion/Osmosis Investigation Set Up (attached, 1 per teacher)
Diffusion/Osmosis Investigation: Student handout (attached, 1 per student)
Vancomycin Card Sort (attached, 1 per student)
Cell Venn Diagram handout (attached, 1 per student)
Animal, plant, and bacteria cell models (optional)
Below are the materials needed for the investigation (amounts vary):
Glucose testing strips
Gloves and goggles
Deionized or distilled water (Do not use tap water!)
Starch (cornstarch or potato starch)
Iodine (as iodine/potassium iodide, e.g., Lugol’s Iodine)
Beakers (250 mL, 500mL)
Small container (e.g., small paper cup, specimen cup, small beaker)
Introduce the lesson using the attached Lesson Slides. Display slide 3 to read aloud the Essential Questions: How does the cell membrane help cells maintain homeostasis? How does vancomycin work to destroy MRSA bacteria? Display slide 4 to go over the Lesson Objectives. Review these slides with students to the extent you feel necessary.
Display slide 5. Have students label their Cell Venn Diagram handout to match the slides.
Display slide 6. Show students models of animal, plant, and bacteria cells and ask them to fill in a three-way Venn diagram describing the features of each cell.
Display slide 7 and show students this video of E. coli bacteria exploding in the presence of penicillin. Be sure to let them know the left side shows the effects of penicillin and the right side is the no-antibiotic control. Do not tell students why it happens. Instead, move to slide 8 and ask them to look at their Venn diagram and address the following prompt:
How could antibiotics like penicillin be used to kill bacteria without harming the cells of the infected organism?
Ask students what possible consequences could occur if a cell wall is damaged. Draw their attention to the plasma membrane (also called the cell membrane) which surrounds all of the cells and ask them to recall what the plasma membrane does. Encourage them to consider why plant and bacteria cells need this membrane if they already have a cell wall. It is fine if they do not have a correct answer, but they should offer some ideas.
Display slide 9. On this slide, you can insert the materials and amounts of what you need for the lab. Tell students they will use a model to investigate how the plasma membrane works. Pass out the Diffusion/Osmosis Investigation: Student handout. Direct students to gather their materials and get set up for the investigations as is appropriate to your classroom.
Display slide 10. Insert directions for the investigation. Go over the instructions with the students. Detailed instructions for completing the investigations are included in the student handouts, but it is advisable to walk the students through the methods before turning them loose to complete the work on their own. The Diffusion/Osmosis Investigation Set-Up handout has additional set-up instructions and teacher facilitation notes.
It is best to have students complete the Semi-Permeable Membrane Demonstration for themselves. If, however, time is a serious concern, it can be done as a teacher demonstration. During the 15-minute wait time in the demonstration, introduce the Dialysis Experiment. If students are deciding on glucose concentrations for themselves, have them choose and calculate the necessary quantity of glucose and water at this time (see Teacher Notes on test sensitivity in the Diffusion/Osmosis Investigation Set Up).
After completing each investigation, display slide 11 and have students answer the analysis questions on their lab handout.
Display slide 12. As a class, review the post-investigation questions for each activity. See the note below for additional probing questions to help students draw conclusions about how the semi-permeable membrane works.
Go to slide 13 to reinforce the idea that the size of the molecule is related to whether or not it can pass through a semi-permeable membrane.
You may consider displaying slide 15 for student to take notes in a less structured Star Notes strategy to organize the upcoming information. Encourage them to specifically add details about how the lab connects to the new concepts.
Go through slides 16-22 and briefly cover the following information:
Slides 16-18: Brief review of the fluid mosaic model.
It is okay if students can’t remember hydrophilic and hydrophobic as long as they understand that the lipid bilayer separates the water inside from the water outside of the cell.
Slide 19: Passive transport (simple diffusion: solutes, osmosis: solvent).
The two investigations demonstrate passive transport (diffusion and osmosis).
Slide 20 Show this video. It shows a very simple animation of both processes (play to 0:57).
Slide 21: (Hidden slide) Passive Transport supporting video. (See Teacher’s Note below.)
Slide 22: Facilitated diffusion.
Slide 23: Tonicity (hypo-, iso-, hypertonic).
Ask students to identify under what conditions passive transport occurs.
Have students add the tonicity diagrams in addition to their written notes, taking care to include labels and draw arrows in the correct directions.
Slide 24 and 25: Hidden slides with Osmosis and Water Potential and Cell transport supporting video. (See Teacher’s Note below.)
Before continuing, pause and display slide 26 to have students answer the first Essential Question: "How does the cell membrane help cells maintain homeostasis?" from their Cornell Notes "summary" or as part of their "add" in STAR notes. It is recommended that students write this individually before having a class discussion about the answer.
Display slide 27 and return students’ attention to the exploding E. coli video from the Engage. You may want to show it again to refresh their memory. Ask them how passive diffusion through the plasma membrane could be related to what happened to the E. coli in the video.
Display slide 28. Continue by introducing students to MRSA (methicillin resistant Staphylococcus aureus) as strains of S. aureus that have developed resistance to the antibiotic methicillin. Methicillin is an antibiotic similar to penicillin, which is used to treat E. coli infections. Due to the resistance of S. aureus, doctors have to prescribe vancomycin, a stronger antibiotic with more serious side effects, to get rid of a MRSA infection. Tell students that they will be figuring out how vancomycin kills MRSA.
Display slide 29 and introduce students to the Card Sort instructional strategy. The activity can be completed independently or in groups of 2-3. Provide each student with a set of the Vancomycin Card Sort Cards. Students should sort the cards to map out the major steps of vancomycin’s mechanism of action. Make sure they know that there is a missing step, and they should identify where the gap appears in the card order. Prompt them to think about what they have learned about passive transport while they work through the card sort.
Once most students have completed the Card Sort, display slide 30. Ask them to discuss what role passive transport plays in the process within their groups, or with an Elbow Partner, if students worked independently.
Display slide 31 and inform students they will be working to answer the second Essential Question.
Display slide 32. Have students work independently for the final activity. Using the cards from their card sort, students will create a Cognitive Comic. Students should draw their own "card(s)" or panels to fill in the gap in the card’s explanation. A comic strip format is the most straightforward but see the Teacher’s Note below. Students' added card(s) /panel(s) should illustrate how passive diffusion works as part of vancomycin’s mechanism and should include a caption to support their art. Some students will be uncomfortable with drawing because they worry about it being "bad." Assure them that they are not being assessed on their skill and emphasize that they can and should use their caption to explain anything they think their picture does not make clear.
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