Investigating Properties of the Cell Membrane with Soap Bubbles

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Objective

SWBAT identify and discuss the structures and functions of the components within the cell membrane

Big Idea

Use bubbles and straws to investigate the properties of the cell membrane in this engaging and self-directed activity!

Notes for the Teacher

I stumbled upon this lab when my department members and I were feeling like we needed to update our cell labs to incorporate a fresh approach to our content, one that was different from the typical diffusion lab using dialysis tubing.  

As is often the case in the world of secondary teaching world, the original source of this lab activity is unknown, the lab worksheet is credited to teacher Jeremy Conn.  He has also created a great slide presentation that outlines the steps of the lab.  These slides were really helpful for me as I worked with the bubbles on my own prior to piloting the lab in our biology classroom.  I did not share the presentation with students.  At this point in our year together, I can and do expect that students are willing and able to dive into lab procedures with confidence, care, and precision. However, I could see using the slides with students who might be struggling with the scientific concepts as a follow up after the lab session as a concept review.  I found that I didn't have to with my students this year for the pilot run because one student was so excited about the work that he went home and repeated the experiments and took photos of his lab work that we used together in class as we discussed the major concepts behind the lab.  

What I loved about this lab is that it is in essence an inquiry activity that students can do with very little guidance and without a huge amount of prior knowledge in order to make hypotheses and connections between what they see using the bubbles and the basic properties of cell membranes.  Students were focused throughout the activity, had fun using the bubble solution and straws, and were able to ask each other questions based upon their lab document in order to reach conclusions about the structure and function of cell membranes.  

The Classroom Flow: Introducing the Lab

10 minutes

1.  Ask students to look at the following prompts on the board and discuss them briefly in their groups.

What is the cell membrane made up of?  What does it look like?

What does the cell membrane do?

2.  Using the spokesperson protocol, have students share out their responses.  Students will be able to tell you that the cell membrane is made up of lipids (some may be able to use the term phospholipid bilayer) and that its main job is to protect the cell.  

3.  Tell students that today they will be exploring some of the properties of the cell membrane and that together over the next few days you will be exploring specifics of cell membrane structure and function.  

4.  Pass out the Cell Membrane Bubble Lab document.  Give students 1-2 minutes to read through the directions.  Then go over the major points:

  • Students will be using bubble solution, trays, and straws to create simulated cell membranes.  Point out where students can find the materials in the classroom.
  • Students will follow the directions for each simulation, discuss what happens, and write out their explanations for what they do/see and the ways it connects to the actual cell membrane.

The Classroom Flow: Working with the Bubbles

30 minutes

1.  Students should take about 5 minutes to get their materials and settle in at their lab tables.  

2.  You will see many great examples of positive collaborations and focused, engaged group work like:

  • Students reading directions out loud together.
  • Students assigning roles or volunteering for specific tasks.
  • Students getting additional materials.
  • Students collaborating with other groups for tips about the best procedure for bubble blowing.
  • Students consulting with you for additional procedure tips. 
  • Students repeating experiments to confirm their results.  
  • Students reading their responses out loud to their lab groups for confirmation and critique.

3.  While students are working, observe group collaborations closely and be available for additional materials and suggestions for bubble technique alternatives. 

  • Note:  In general, students will not need help with the lab directions or lab document explanations.  As much as possible, I tend to stay as uninvolved with group work as possible.  I will suggest that students check in with specific lab groups that I have observed having a successful experience with specific lab protocols.  As students work, I find that they want to share their successes with me and my main job is to observe, connect, and admire whenever possible.  Asking students to repeat a demonstration using the bubble solution can lead to many interesting conversations by asking specific prompts like "Why do think that is happening?" and "How do you think this might be like what happens in a cell?"  Turning the conversation back to the students is my main priority; there is plenty of time in the upcoming days of the unit to direct technical discussions about cell membrane structure and function.  

4.  One of my students performed all of the activities at home and took color photos.  Check them out to get an idea of what you and your students can expect as you work with the bubble solution and create frames out of straws.  

The Classroom Flow: Wrapping Up

10 minutes

1.  Ask students to discuss the following prompts:

What properties of cell membrane phospholipids did you visualize using our bubble activity?

What surprised you about this activity?  

2. Use the spokesperson protocol to share out responses.  Students will tell you how surprising it was to put their hand through the bubble and pull it out with the bubble still intact.  They were also excited to see the string circles form holes in the bubble surface.  They will be able to tell you that the bubble lab simulated the phospholipid bilayer structure, that the string circles were like channels through the cell membrane, and that the bubble division is an analogy for binary fission in bacteria.  This lab activity is a great one to refer to later on as you explore each of these characteristics throughout the unit too help students visualize each property.  Alternatively, each demonstration is so simple, you can quickly show it to them using the bubble solution and straw structures as you discuss each membrane characteristic throughout the unit.    

3.  Remind students of their lab document due date before the class session ends.  Take a look at the following three student work samples below.  All three samples make it clear that the students understand the concept of the fluid mosaic model of the cell membrane both in their responses to lab document prompts and through their diagrams on the last page of the handout.

Student Work Sample 1

Student Work Sample 2

Student Work Sample 3