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Introduction to cytoskeleton

Video transcript

let's talk about the cytoskeleton and when we look at the word we see skeleton and the prefix cyto means cell so cytoskeleton simply means the skeleton of the cell and although pretty much all cells have some form or another of a cytoskeleton we're going to focus mainly on the cytoskeleton that's found in animal cells so the cytoskeleton in cells serves purposes that are actually very similar to the purposes that our skeleton serves in our body so the first thing is the cytoskeleton provides structural support number two the cytoskeleton helps with the movement and number three it helps with the transport of substances within the cell these are the three basic functions of the cytoskeleton but as we go along there are a couple of others that are going to come up as well so now let's take a look at a cross-section of a cell and let's orient ourselves and label this diagram so right over here we have the cell membrane then we have some mitochondria we have the endoplasmic reticulum and you can see it's dotted with these blue things those represent ribosomes and finally let's get to the structures of the cytoskeleton so we're going to go through the very structures explain briefly what each of them do and then afterwards we're going to go into each one separately and in more detail the first structure we're going to mention are these green tubes that you see these are the microtubules and they have a diameter of approximately 25 nanometers and the microtubules are involved in a number of things they're involved in the mitotic spindle if you're not sure what that is we're going to discuss it in more detail later the microtubules also make up cilia cilia are these hairlike projections outside of a cell that will help to sleep substances across the outside of the cell they also make up flagella flagella are these tale-like structures that are outside of a cell and help move it and again if you're not really familiar with this don't worry we're going to go into it in more detail soon and microtubules also help with transport of substances within a cell the next structure we're going to talk about are these blue fiber like things they are the intermediate filaments and they have a diameter of approximately 10 nanometers and I want you to take a look at the diagram that's a cross-section of a cell and see if you could maybe figure out what the purpose of the intermediate filaments is so the intermediate filaments basically provide structural support to the cell and maybe a way to help you think about this is we can compare this picture that we're looking at to a mattress so we'll say that the cell membrane on either side is kind of like the top and bottom of a mattress and let's say that mattress was filled only with air maybe some other stuff that we're really not hard and if you sat on the mattress maybe there's a hole somewhere the mattress some of the air might come out and then when you got up the mattress might be in a very flattened position however most mattresses have these metal Springs and sides so you sit in the mattress you know gets a little bit flatter but then when you stand up the mattress goes back to its original position so those Springs inside are providing structural support so the intermediate filaments provide structural support in a very similar way we can see that they help resist mechanical stress and help the cell retain the shape that they're supposed to have in a way that's very similar to the springs in the inside of a mattress and the last structure we're going to mention are these purple tubes they are the microfilaments and they have a diameter of approximately seven nanometers and just keep in mind that microfilaments intermediate filaments and microtubules are all made out of protein and microphones are involved in movement of the cell and this is a movement that's different than the movement that would be provided by cilia and flagella cilia and flagella are both outside of the cell and microfilaments health movement of the entire cell from within so let's give two examples of this one example is during cell division the cell will turn into something that looks like this so it's going to be kind of pinched in the middle and then eventually it'll separate into two separate cells so how does the cell kind of move in that way and form the interesting shape well with the help of the microfilaments another example of this would be amoeba and amoeba it's not exactly an animal but we'll mention it anyway so an amoeba has these projections known as pseudopods and it will engulf a piece of food between you know the pseudopods will kind of reach out and gulf a piece of food and that's how to ingest food but how do those pseudopods move with the help of microfilaments and this applies to other cells that are not necessarily amoeba but move like amoeba and have pseudopods they also move with the help of microfilaments