Give your students the experience of making the Cell Membrane! This hands-on approach has really helped my kids understand the structure of the cell membrane, the function of transport proteins, and the types of membrane transport!
There are a handful of Biology topics that just seem hard for students to understand. The structure of the cell membrane is one of them! In order to make the membrane real – students needed to make the cell membrane! I began using this approach a few years ago and immediately noticed that students had a better grasp of how the cell membrane works.
Make the Phospholipids:
Take a length of pipe cleaner (about 3 inches), slip a pony bead into the middle, twist the pipe cleaner one time to keep the bead from falling off.
Vola! You have a phospholipid – complete with phosphate head (the bead) and two lipid tails.
Now make a ton of them – or have a student helper or parent(s) make a ton of them! You will need about thirty phospholipids per set. Place each set into a ziploc bag for easy distribution to students.
Students can work individually, but I prefer to have students work in pairs. This gives them a chance to bounce ideas off each other as they create their membranes.
Start by having every student hold up one phospholipid. Ask them to identify/point to the phosphate head and lipid tails. Then challenge them to arrange the molecules into the form of the cell membrane. This is a great time to reinforce the idea that the lipid tails are hydrophobic and ‘hide’ between the phosphate heads!
They are ready for the rest of their materials to make the Cell Membrane:
- Half a toilet paper tube
- One clothespin
- A quarter sheet of paper (scrap paper is fine)
Students will rip the paper into approximately 1 inch square pieces (does not have to be perfect, as you can see from my example!). Roughly half of the pieces are then crumpled into tiny balls.
Now it is time for students to set up each situation for cell membrane transport!
Passive transport: Simple Diffusion
Establish a concentration gradient with many small wads of paper on one side of the membrane and just a few on the other. These small wads will represent small non-polar molecules like CO2 and O2. Students will model passive transport by bringing the wadds through the membrane between the phospholipids from high concentration to low concentration.
Passive Transport: Facilitated Diffusion
Establish a concentration gradient with the larger (uncrumpled) pieces. These will represent larger molecules like glucose. Point out that larger (or polar) molecules can not pass between the phospholipids. In order to come across, they need a tunnel! The half toilet paper tube represents a protein tunnel. Students model Facilitated Diffusion by bringing the pieces of paper through the protein tunnel.
Active Transport: Protein Pump
Using the small pieces again, set up a gradient across the membrane. This time, while we have a lot of molecules on one side of the membrane, the cell needs even more of those molecules, increasing the concentration on one side. This requires active transport! Students model active transport by ‘actively’ using the clothespin. They will grab and move paper from the side with lower concentration to the side with higher concentration.
Recording what they learn:
Students can record what they have learned in several ways.
Take pictures and annotate: Students can use a device and take a picture of their models. Photos can be put into a Google Slideshow, which will allow students to label important parts of the model (a single phospholipid, which side has high vs low concentration of molecules, the type of transport being modeled etc).
In their notes: Provide a place in student notes to draw out their models and label important parts. It may be helpful to provide the phospholipid bilayer in the notes. The cell membrane itself takes a long time to draw! But they can add the molecules and transport proteins, along with labels for their diagrams.
Giving Instructions For How to Make the Cell Membrane
Here are a few ways to lead students through this activity. Choose what works for your classroom and students.
Watch you, do it. Guide the whole class through each type of transport, one at a time. Model how to make them by showing and explaining photos of each type. Or make the models while they watch using a document camera or video connection between your device and the board. Once students see it, they can then make it!
See it, do it. Create written instructions with pictures of the models. Students follow the instructions and complete their own models. Instructions can be printed or digital. You may choose to do the models one at a time, bringing the class together between each one to check for understanding. Or give them all of the instructions all at once and let them go!
Find it, do it! Tell students you want them to use the given materials to model Simple Diffusion, Facilitated Diffusion and the Protein Pump. Let them use their notes, text book, and/or internet to find examples of each type, and figure out how to model it.
Digital Membrane Transport Activity
In 2020 when our school went to distance learning, I made a digital replacement for this activity so my students could make a cell membrane at home. It worked great!