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Cell Membrane Activity
Summary/Abstract: Cell biology is an integral part of most high school
Biology courses. Students are asked to learn about cell structures and
how they function in a variety of ways, ranging from memorization, to
microscope work, to actual lab experiences. The importance of the
cell membrane is usually stressed, but is hard to visualize for most 10th
grade biology students. This activity provides a macroscopic model
that mimics the cell’s phospholipids bilayers using soap bubbles in an
innovative, motivational and inexpensive way. Students can explore
for themselves how a cell membrane might work and how its structure
is related to function.
Materials Needed (per group):
• Newspapers
• 2 straws
• Cotton thread
• Scissors
• Pencil or pen
•
•
•
•
Tray
Bubble solution to depth of
1-2 cm
Paper Clip
Ruler with metric side
Procedure:
1. Work in groups of 2.
2. Pick up your materials (see list above).
3. Spread newspapers on top of the table and floor around where you
are working.
4. Your Teacher will demonstrate how you are to operate your cell
membrane model
DEMONSTRATION 1: Fluidity Model
The theory of the structure of the cell membrane is called the
“Fluid Mosaic Model” of the cell membrane. This means that the cell
membrane is made up of many small molecules that are moving around
and changing constantly.
TO SHOW THIS:
Let the lights shine off the bubble surface and look at the movement you
see within the bubble. What are the soap molecules doing?
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Demonstration 2: Flexibility
Within a lipid bilayer, molecules can move freely around and reorganize
themselves into almost any type of shape.
TO SHOW THIS:
Twist your looped string in opposite directions into different shapes.
What happens to the soapy film?
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Demonstration 3: Self-Sealing
Remember that the membrane is not a solid. Some small molecules can
pass through it.
TO SHOW THIS:
Take a DRY Pencil or Straightened Paper Clip. Stick the pencil or paper
clip into the soapy membrane so that it passes through to other side. Did
the membrane seal around the pencil and clip and stay intact? ________
Next take the pencil or paper clip and dip it into the soapy solution. Why
do you think the pencil or paper clip must be coated with soap solution in
order to pass through the membrane?
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Demonstration 4: Membrane Proteins
In a cell membrane, small molecules, such as water, may move through
the membrane. Larger molecules cannot pass through the cell membrane.
The only way these large molecules can get into the cell is through
protein channels.
TO SHOW THIS:
Take a small loop of thread. Dip it into the soap solution. Carefully, stick
the looped thread onto the soapy membrane. Now pop the bubble inside
the looped thread. You have just made a channel protein.
Name: _________________
Block: ______
Cell Membrane Activity Answer Sheet
DEMONSTRATION 1: Fluidity Model
1. What are the soap molecules doing?
Demonstration 2: Flexibility
1. What happens to the soapy film?
Demonstration 3: Self-Sealing
1. Did the membrane seal around the pencil and clip and stay intact?
2. Why do you think the pencil or paper clip must be coated with soap
solution in order to pass through the membrane?
Conclusion Questions: Use pages 175-177 in your book and the
knowledge you learned in today’s activity to answer the following.
1. What is the structure of the cell membrane and what unique
properties does it have?
2. How to these properties relate to how it works?
3. What are three ways that the model we made today is like the real
cell structure?
4. What are two ways that the model we made today is different than
the real cell structure?