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Current time:0:00Total duration:5:29

Video transcript

in this video we're going to explore a little bit about membrane dynamics so we know that in our fluid mosaic model of our cell everything in the cell membrane moves around so our cholesterol moves around and our phospholipids move around and our proteins all move around but in this video we're actually going to focus in on our phospholipids so over here I pre drawn a picture of our cell membrane now you notice that these phospholipids are really tightly packed together so how do these lipids these phospholipids actually move in our cell membrane well before we get into answering that question we're just going to quickly label our cell membrane so out here we have our extracellular this is the outside of our cell and in here we have our intracellular or the inside of the cell and there's an important distinction that we have to make between intra and Inter cellular intracellular is the inside of the cell while intercellular is between cells I like to remember this by thinking about the word intercontinental that means between continents so intercellular must mean between cells we sometimes call the phospholipids that border the extracellular environment as the outer leaflet and we call the phospholipids that border the inside or the intracellular environment as the inner leaflet and it'll set the cell membrane that we've drawn is very basic we've taken out all the cholesterol the proteins and all of the other stuff that makes up the cell because in this video we're actually no focus in on the phospholipids themselves so the first type of movement is uncatted eyes this means that there's no need for a catalyst so one type is we can actually have a phospholipid on the outer leaflet move onto the inner leaflet or we can have it in reverse we can have something on the inner leaflet move to the outer leaflet we call this trans bilayer diffusion and this actually has a nickname which we call flip-flop and this type of movement is really slow there's no cat list and you're trying to move and you're trying to move a phospholipid from one leaflet to the other so this process is very slow it doesn't happen that often now there's another type of movement where we can have a phospholipid like this actually move side to side and this is what we call lateral diffusion and just to give a bird's eye view of what this actually looks like if we actually have the head of our phospholipid the movement is not just from side to side but it goes all around the cell membrane so if we were to look at this from the top this phospholipid can move in any direction so we call lateral diffusion and since we're not actually switching between leaflets in this type of movement this is actually pretty fast and it happens a lot in our cell membrane so if we have uncatted eyes movement naturally we will have catalyzed movement and since this movement is catalyzed we're going to need a catalyst and in this case our catalyst will be a protein the first one we're going to talk about is we can have something on the outer leaflet like this actually flip to the inside kind of like our trans bio layer diffusion but this time it's aided by a protein a catalyst and not only so this process actually uses ATP which we call adenosine triphosphate just remind us ATP breaks down into adenosine diphosphate ADP with a phosphorus and this provides energy for this reaction to happen this catalysts that we used or this protein is actually called flip base and this is pretty fast compared to our trans bilayer diffusion and the next one we have again also uses a catalyst so we have another protein this particular protein is called flop ace and flop ace also uses ATP now what flop ace does is it actually brings a phospholipid on the inner leaflet to the outer leaflet so it does the opposite of what flip base does and again this is also pretty fast because it uses a catalyst now the last one that is catalyzed does something really interesting it actually brings some a phospholipid from the inner leaflet to the outer leaflet and one from the outer leaflet to the inner leaflet and this is what we call scram blaze and this actually does not need ATP doesn't require that extra input of energy and again because it is catalyzed it is pretty fast so in summary these are the ways that allow our phospholipids to actually move around our cell membrane and create this amazing moving fluid cell membrane structure that we call the fluid mosaic model