[Music] hi it's Mr Anderson and in this podcast I'm going to give you a brief overview of the cell membrane uh you probably learned growing up that the function of the cell membrane is to regulate what comes into and what goes out of the cell it's over simplifying a little bit but it's a pretty good definition and so you may ask yourself why do you have a picture of a musox here well the reason why is that when I ever talk about the cell membrane I like to talk about the muskox and how it's a whole heck of a lot like this over here this thing over here is called a phospho and the reason it's phospho is because we have a phosphate group right up here in the head it's called a phospholipid and the phospholipid basically has two parts to it up here it's going to have a Charged part so it's going to have a negative charge up here and then the tail end this lipid part or or that's a fat part since it has so much carbon carbon carbon with hydrogen around the outside it's non-polar this whole rear end is going to be nonpolar what does that mean well this end over here loves water and this end down here hates water you know that if you've put oil which is similar to a lipid in structure in water it just doesn't mix and so basically the head is going to love water tail is not we call a molecule like this amphipathic and so basically why is this like a musx well if you throw a bunch of muscs together and then you have a predator show up the heads of the MUSC are gonna face the Predator because the heads of the MUSC love a fight and they want to fight that Predator now the tail of a muskox is going to protect the baby muskox that are going to sit on the inside and so basically they'll form a ring around whatever they want to protect and that's because a MUSC is amphipathic if we look at those uh phospholipids then they're going to be the same way in other words the heads are all going to face the water and then the tails in here are going to be aw from the water and so what you get is a membrane this would be a single layer of phospholipids this would be a b layer right here and so basically all the cells period all the cells that we have have a cell membrane and all of those cell membranes do the same thing they regulate what comes into and out of the cell now the model we use to explain how a cell membrane works is it is a fluid mosaic model and so let me get a color that you can see so it's a fluid mosaic model if we break down this word it's fluid and that means that all the material inside the membrane is actually moving around and if it ever stops moving then it doesn't function as a membrane and the other thing is that it is omaic and so it's made up of a lot of different things what are the major things that it's made up of well you can see here's those phospholipids those are forming this membrane but the big blue things are going to be proteins and so the two major parts of a membrane are going to be the phospholipids which are the red things and then we're going to have proteins uh what's the function of the phospholipids those basically keep water on either side and so it makes the structure what's the function of the proteins well those actually give proteins their specific um characteristics and so it allows material in it connects to material outside and so if you to get your head around this the cytoplasm is going to be down here so this would be the cytoplasm and this is going to be the cytoskel and attached to it and then the extracellular fluid is going to be on the outside now there are a few other things that you can see inside here we've got this folded protein we've got right up here I can see this right here is called let me get rid of some of that this is called a glyco protein glyco means that it's got protein on the inside but it also has a sugar attached to it we're going to have glyco lipids um we're going to have a number of things like here would be cholesterol but basically when you're thinking about a membrane the function of it is to keep material on either side and it has to maintain its fluidity and so all of these things are moving these phospholipids are moving horizontally they're floating around and I've seen some neat animations of this it's think of it as like a sea this thing is whole floating and all of these proteins are like floating around inside it as well now it's attached to the cytoskeleton and to the outside to this extracellular Matrix but it's really in flocks um and then the characteristics are going to come from the proteins what it does so if we talk more about that phospholipid itself the phospholipid again has a hydrophilic head has a hydrophobic iic tail um and they float back and forth if they get too close together that's bad and so what they lots of times will'll have is a kinky tail an unsaturated lipid tail and that kind of keeps them apart sometimes if it gets too cold the cholesterol will actually keep them from getting too close and if it gets too warm as they start to drift apart the cholesterol kind of hold on to it and keep it there but the function of this is to allow the movement of material so oxygen needs to get into a cell it's going to do that through diffusion and carbon dioxide is going to get out so what actually moves through a cell well the only things that can really move through a cell are going to be things that are uncharged or things that are really really small but really things that are uncharged and so how does oxygen get in it can diffuse in because it doesn't have a charge carbon dioxide out the same way but even things that are water that are really really small they can't get in or glucose can't get in it actually has to move through proteins and so what do proteins do proteins allow material into and out of the cell so we'll talk more about how this actually works but how does water get into a cell then we used to think that it would just flow in using osmosis but we now know that you have these proteins called aquaporins and basically what they do is they will allow water to move through moves through really really quickly uh but sometimes we'll make proteins that actually have this area on the inside where it's protected and that allows the the material to move through that has any kind of a charge so that would be like glucose moving through here and then we have some of them that'll move through using a process of uh active transport where we put energy in to move them apart or facilitated diffusion so we've got a lot of different things going on but if you can remember that a cell membrane is in all cells it's it's fluid it's always in movement and it's really made up of two things phospholipids and proteins uh you've got a pretty good start and I hope this is helpful