In this video, we're going to begin our lesson on cell junctions. It's important to note that neighboring cells of eukaryotic organisms can directly interact with one another using cell junctions. There are four main types of cell junctions used to link adjacent cells together. Below, we have a table that lists each of these types of junctions in the left column and then it has a description of each junction in the right column. Further below, we have images of each of these four junctions. Notice that the first three junctions in the first three rows of this table correspond with junctions found in animal cells, and the very last junction in the table corresponds with the junction found in plant cells, which is important to keep in mind.
The very first junction that we have in this list is the tight junction. As its name implies, the tight junctions hold cells very tightly together, creating a leak-proof barrier. These tight junctions are composed of membrane proteins that link cells tightly enough to create these leak-proof barriers. When you drink a glass of lemonade, the tight junctions prevent the lemonade from seeping right between your cells and ending up on the floor. In our image below on the left-hand side, you'll notice the tight junction. Each of these blue squares in the background represents the membranes of two adjacent cells. The tight junctions utilize protein structures in orange to hold the two cells very tightly together, forming a leak-proof barrier that retains liquids on one side.
The next junction we have is called anchoring junctions, otherwise known as desmosomes. These anchoring junctions or desmosomes consist of intermediate filaments that anchor neighboring cells together using complex protein structures. In the next image, you can see the anchoring junction. Once again, this junction uses a complex protein structure to hold the two adjacent cells together. The anchoring junction is not necessarily leak-proof, so liquids are able to seep their way in between, which distinguishes them from the tight junctions.
The next junction is the gap junctions. As their name implies, gap junctions create protein channels that form a gap between the two cells, thus connecting the cytoplasm of the two neighboring cells, specifically in animal cells. In the image below, this junction in blue is the gap junction. Notice that the gap junction creates these protein channels or tunnels that are directly linking the cytoplasm of the two neighboring cells, allowing the cells to exchange nutrients and other substances.
The last junction we will discuss is the plasmodesmata, a junction of plant cells and analogous to the gap junctions. The plasmodesmata create gaps in the cell walls of plant cells that connect the cytoplasm of two or several neighboring plant cells. In the image on the far right-hand side, you'll see multiple plant cells with plasmodesmata, which are gaps or openings in their cell wall that allow the neighboring cells to exchange nutrients. This can be beneficial to these plants in many different ways.
This concludes our brief lesson on cell junctions, and we'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.
