Cell Junctions - Video Tutorials & Practice Problems
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concept
Cell Junctions
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Video transcript
In this video we're going to begin our introduction to cell junctions. And so neighboring cells of eukaryotic organisms are able to directly interact with one another by using cell junctions. Now, really, there are 4 main types of cell junctions that you all should know that link adjacent cells together. And so notice down below here, we're showing you this table of the 4 types of cell junctions that you all should know. And so 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. And then down below what we have are some images of each of these 4 junctions. And so the very first junction that you all should know are the tight junctions, which are going to be membrane proteins that link cells together in a tight fashion in order to create leak proof barriers. And so when you drink a glass of lemonade, that lemonade does not leak in between your cells and end up on the floor. And that's all thanks to tight junctions, which create leak proof barriers. So if we take a look at our image down below over here on the left hand side, notice that we're showing you an example of a tight junction. And so notice that each of these yellow, barriers that you see here and here represent the plasma membrane of 2 different cells. And, here in the gray circles that you see, these are representing proteins that are tightly linking these 2 cells together to create a leak proof barrier. So that way, liquids cannot really make their way, and leak in between the cells because they're so tightly held together. So liquids will not be able to seep through and once again, tight junctions create a leak proof barrier. Now the second type of junctions you all should know are the anchoring junctions or in other words sometimes referred to as desmosomes. Now the anchoring junctions are intermediate filaments that as their name implies with the anchoring are going to anchor neighboring cells together using complex protein structures. And so down below here, you can see that we're showing you an image of anchoring junctions also known as desmosomes. And so you can see that they use these complex protein Now what you'll notice is that anchoring junctions, Now what you'll notice is that anchoring 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. Now moving on, the 3rd type of cell junction that you all should know are the gap junctions, which as their name implies, these are protein channels that are going to create a gap between 2 cells. So they are going to connect the 2 cytoplasm of 2 animal cells. And so when we take a look down below, over here, notice that we're showing you an example of gap junctions. And so notice that these are going to be proteins that literally create channels between the two, cytoplasm of 2 neighboring cells. So once again, the 2 yellow, barriers that you see here represent the cell membranes of 2 neighboring cells. And then the protein channels that you see here, notice that they're literally creating a, a pore or a gap between the two membranes so that they can exchange nutrients and things of that sort. And so what's important to note is that the first, three junctions that we talked about, the tight anchoring and gap junctions are all only found in animal cells. And so then the question becomes, well, what about plant cells that have cell walls? How do they create cell junctions? And so that's exactly what this 4th and last junction is all about, the plasmodesmata. And so these plasmodesmata are basically the plant version of gap junctions. And so plasmodesmata are going to be gaps in the cell walls that connect the 2 cytoplasm of 2 neighboring plant cells. And so once again, the plasmodesmata are specifically found in plant cells, whereas the other 3 here, the type, the anchoring, and the gap are all found in animal cells. So if we take a look at our image down below of the plasmodesmata, notice that we're showing you 3 neighboring plant cells right here, and they have gaps in their cell walls that we're showing you here, that basically allows these, cells these plant cells to exchange nutrients with one another, in this type of fashion, connecting the 2 cytoplasm or or all of the cytoplasm of the neighboring plant cells. That is what plasmodesmata allow for. And so this here 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. So I'll see you all in our next video.
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Problem
Problem
Which of the following are only in plant cells and not in animal cells?
A
Gap junctions.
B
Desmosomes.
C
Plasmodesmata.
D
Tight junctions.
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Problem
Problem
Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through: