Semipermeable Membranes' Role in Cell Communication

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  • 0:01 A Flexible Boundary
  • 0:44 Receiving Signals
  • 1:37 Examples of Cellular Processes
  • 3:27 Cell-Cell Recognition
  • 5:00 Lesson Summary
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Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Your body is made up of cells, which depend on signals from other cells in order to function properly. Believe it or not, the cell membrane is one of the most important players in this communication, ensuring that messages are received and decoded properly.

A Flexible Boundary

Your cells are incredibly small - so small that you can't see them without help from a microscope. But as small as they are, they are made up of even smaller components, all of which have very important jobs. The very outside of each cell, the cell membrane, separates the inside of the cell from the environment around it.

The cell membrane acts like a traffic cop, controlling what goes into and comes out of the cell. It does this through both the phospholipid bilayer that it is made of as well as proteins that are embedded in the membrane. Molecules that are small enough can pass right through the membrane itself, while larger molecules have to move through the channels provided by the membrane's proteins.

Receiving Signals

Many of the proteins in the cell membrane are involved in cellular communication. They receive chemical messages from other cells called signaling molecules. When these molecules bind with the proteins in the cellular membrane they trigger a change in the protein, which then sends that message into the cell and activates a specific cellular response.

In this way, we can see that cellular membranes and their components are critical to proper cellular communication. It's like being at the airport and having to go through a series of checkpoints. If you show up at the first security checkpoint without your boarding pass and ID, there's no way they're going to let you through to the next checkpoint. Cell membranes provide the same type of service. If the signaling molecule that reaches the cell membrane doesn't match the embedded protein, that signal won't get sent on to the next step.

Examples of Cellular Processes

While the cell membrane is like the wall that separates you from the unsecure side of the airport and the secure side, the membrane proteins that are embedded within it are really what do all of the 'checking.' The variety of membrane proteins can be quite extensive, such as with red blood cells, in which we have identified over 50 different kinds of plasma membrane proteins!

It might help to think of the membrane like your face, and the proteins as your eyes, mouth, and nose. Your face holds all of these components in place, but the components themselves are what actually communicate and receive signals from your environment. The functions of these many proteins are as varied as the proteins themselves. For example, some proteins provide channels for large molecules to pass through that wouldn't otherwise fit through the membrane itself. Others may be enzymes that react to substances and facilitate speedier chemical reactions.

Some proteins are designed to recognize membrane proteins of other cells and communicate that way. Yet, other proteins are designed to hook into proteins of other cells, connecting the two cells together. And, as mentioned, many cell membrane proteins are designed to fit specific signaling molecules, which trigger a relay of that signal or message down through the cell itself.

Because there are so many functions to perform, many cell membrane proteins are multi-taskers. For example, certain proteins are designed to bind to the extracellular matrix (the ECM), which helps maintain the cell's shape and stabilize other membrane proteins. But this binding also transmits a signal into the cell for certain cellular processes. In this case, the protein is both providing structure and facilitating cellular communication.

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