Cell Membrane Activity - Weebly

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? ______________________________________________________ ______________________________________________________

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? ______________________________________________________ ______________________________________________________

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? ____________________________________________________ ____________________________________________________

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?

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