In this video, we're going to begin our introduction to cell junctions. Neighboring cells of eukaryotic organisms are able to directly interact with one another using cell junctions. Now, really, there are 4 main types of cell junctions that you all should know that link adjacent cells together. Notice down below here, we're showing you this table of the four types of cell junctions that you all should know. You can see the junction type over here on the left-hand side and then the description of each of the junctions over here on the right-hand side. Down below, we have some images of each of these four junctions.
The very first junction that you all should know are the tight junctions, which are membrane proteins that link cells together tightly to create leak-proof barriers. When you drink a glass of lemonade, the lemonade does not leak between your cells and end up on the floor, all thanks to tight junctions which create leak-proof barriers. Looking at our image down below, on the left-hand side, notice that we are showing you an example of a tight junction. The yellow barriers represent the plasma membrane of two different cells. The gray circles represent proteins that tightly link these two cells together, creating a leak-proof barrier. This means that liquids cannot seep between the cells because they are so tightly held together.
The second type of junctions you all should know are the anchoring junctions or sometimes referred to as desmosomes. Anchoring junctions are intermediate filaments that, as their name implies, anchor neighboring cells together using complex protein structures. Down below, you can see that we are showing you an image of anchoring junctions, also known as desmosomes. These junctions may not be leak-proof, so things can still seep in between the cells, unlike tight junctions, which are so tightly held together that they are leak-proof.
Moving on, the third type of cell junction that you all should know are the gap junctions. As their name suggests, these are protein channels that create a gap between two cells. They connect the cytoplasm of two animal cells. Below, notice that we are showing you an example of gap junctions. These are proteins that literally create channels between the two cytoplasm of two neighboring cells. The yellow barriers represent the cell membranes of two neighboring cells. The protein channels create a gap between the two membranes so they can exchange nutrients and so forth.
It's important to note that the first three junctions—tight, anchoring, and gap junctions—are found only in animal cells. What about plant cells that have cell walls? This brings us to the fourth and last junction, the plasmodesmata. Plasmodesmata are gaps in the cell walls that connect the cytoplasm of two neighboring plant cells, serving as the plant version of gap junctions. The plasmodesmata are specifically found in plant cells, unlike the other three. If we look at our image down below of the plasmodesmata, note that we are showing you three neighboring plant cells right here. They have gaps in their cell walls shown here, which allow the plant cells to exchange nutrients with one another, connecting the cytoplasm of neighboring plant cells.
This concludes our introduction to cell junctions, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.
