Cell Membrane Analogies

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  • 0:00 What Is the Cell Membrane?
  • 0:50 Classroom Analogy
  • 1:47 Circus Tent Analogy
  • 2:33 Water Balloon Analogy
  • 3:10 Ocean Analogy
  • 4:14 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson focuses on the cell membrane. We'll go over what the cell membrane is and look at several analogies to help understand it further, then you can test your knowledge with a short quiz.

What Is the Cell Membrane?

Cells are the basic units of life. They were actually named cells because, under the microscope, they look like tiny rooms. Much like rooms make up a building, cells make up our bodies and every other living thing. Cells are, in fact, required for something to be considered alive. Each type of cell in our body is a little different and does a specific job. For example, cardiomyocytes, or heart cells, beat on their own and keep the heart pumping. To do these special jobs, cells need to be protected from the environment, which is the function of a thin, movable barrier called the cell membrane.

Let's explore some analogies of cell membranes to better understand this important cell protector.

Classroom Analogy

Let's go back to the idea of a cell as a room and, in particular, a classroom. When in a classroom, students need to be undisturbed and ready to learn, and the noisy kids walking through the hall on their way back from lunch need to be kept out. The age-old solution is to put up walls. The walls keep the classroom protected and all the parts inside the classroom, like the teacher and the students working. In this way, the walls are like the cell membrane.

But we're not fenced in the classroom forever. Windows and doors let people come and go, and this is also an important part of the cell membrane. The cell membrane is selectively permeable, meaning it only lets certain things in and out of the cell as needed. Students late to class come in, and students needing a sip of water go out. Administrators come in, and maybe some bugs fly out the window. The cell only lets things it needs in and gets rid of things it doesn't need.

Circus Tent Analogy

Next, let's use something a little more fun to compare to the cell membrane: a circus! The circus is a fantastic place with working parts all swirling around inside. There are cotton candy vendors, trapeze artists, jugglers, and more. Each of these players are analogous to the parts that work inside the cell. The cell membrane of the circus is the flexible tent separating it from the outside. Like the classroom walls, the tent keeps out wildlife as well as people that didn't buy tickets. Salespeople at the doors monitor the patrons and only let them in if they have their tickets ready, just as the plasma membrane selectively lets substances into the cell. Waste, like trash, can also leave the circus, just like waste leaves the cell.

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