going to move into some more cell biology stuff today and Thursday um your quiz grad are cooperated this time make sure you check those quizzes out and if you missed something make sure you understand why you missed it because there's nothing worse than taking a quiz and going I wonder what that was about so just make sure you're keeping up on that uh the grades are really good I didn't expect anything less from this group also before before I forget uh your first exam is when Tuesday in class your exam is Tuesday in class that's like a week from today yes is way us yep there always is the it just didn't work last week because canvas lost all your grades so if you open this quiz you'll see what you got right and what you got wrong just right now I may doing it wrong but it says oh I probably well I will check that out it shouldn't you should be able to see everything thing um why it's doing this this semester I have no idea but I can check that on a little 5 minute break um just be aware your exam next Tuesday back to the exam stuff um the format is the same as your quizzes which is why I do it that way so you get practice taking that certain format it's not a format a lot of people are used to um and hopefully you're starting to see the benefit of it which is your grades are usually a lot um higher than they would be because it's not an all or nothing so you don't get punished completely for knowing part of a question but you didn't know all of it so you don't get any credit with the partial grading U multiple aners correct you at least get credit for what you didn't know so it works out in your favor quite a bit towards the end of the semester any questions on the upcoming exam I know it's still a week out yeah oh it's in class so it's paper yeah do we to our ID do you need your Cas SE IDs with you uh yes that would be great because there's um 131 people enrolled in this CL class and I don't know all of you so yes thank you for asking any other questions on that exam type stuff you'll have the full time in the class to take it I don't think you'll need it but you have the full it's like 85 minutes or something like that no other questions on the exam okay then I'm going to get into new stuff for today we're going to talk about the cell membrane and this is considered to be a fluid mosaic a fluid mosaic I bet you've heard this before seen it before what does this even mean what does fluid mosaic mean Mosaic what does that mean dissect it fluid because why it moves it does move and specifically what moves is the phospholipids that make up the cell membrane they're not stuck in any one particular place they can move around in their own leaflet they rarely flip to the other leaflet but they can move around in their own sort of linear plane so fluid it also is sort of squishy you know cell membrane has the basically the composition or consistency of olive oil which doesn't make it sound very structurally effective but it is it's pretty amazing something as flimsy as like olive oil could actually provide a pretty robust barrier between the ECF and ICF but it certainly does Mosaic what does that refer to yeah it's got a bunch of stuff in it the cell membrane has a bunch of components it's not just phospholipids there's going to be Gates channels pumps aquapores proteins that stick on the inside and the outside it's a really busy place and that allows the cell to do everything it needs which is take in nutrients get rid of waste respond to its environment changes intracellular working so that it can suit the cells so there's a lot to be said about a cell n bra so when we think about the function and significance of this cell membrane in other words why do we spend so much time talking about it not just in this class but for sure when you get to human body 2 we'll be talking about it quite a bit um so the function and significance kind of related there is that the cell membrane separates the ICF and that stands for intracellular fluid cytoplasm from the ECF or extracellular fluid it's just a lot easier to write ICF and ECF and it allows cells to regulate their internal environment to some degree they can select what they need to function so on this piece of paper we're going to take a look at the main components of a cell membrane and we're going to see how it actually does all the things a cell needs it to do so first thing we'll look at are major membrane components so these are the ones that are in the highest degree they have the most representation so we won't talk about some of the strange oddities but we will talk about the main components of a cell membrane so I'm going to sort of rearrange this paper so I can get it set up to stries and then we'll take a look at the main components first we're going to go through some vocab this vocab is historically kind of tricky for people um I will use these words a lot and I I don't think there's anything much worse than hearing these words and not knowing what they are and then kind of being afraid to ask like that's a terrible feeling so that's why I'd like to go through all of these um with you so that way we're all on the same page so if you have this printed then you already have these terms in front of you but we will be talking about all of these as we go through this particular piece of paper paper this set of notes so we talked about significance of the membrane just separates ICF from ECF allows the cell to regulate its own environment so that's probably not exactly new information we come down here to these words though these might be kind of new hydrophilic what does that mean loves water Hydro water filic loving so it literally translates to water loving what about hydrophobic water fearing water hating again Hydro water phobic you have a fear of so this is water fearing it does not like to interact with water what about amphipathic what does that mean amphipathic yeah good job it has both hydrophilic and hydrophobic so most phospholipids that make up a cell membrane have a hydrophilic component and a hydrophobic component and so if you've got both you are amphipathic you're you have a component that's water loving and a component that's water fearing so I'm going to be sort of brief with this but a component that's hydrophilic or water loving and another that is hydrophobic so when you've got both hydrophobic and hydrophilic Parts you are amphipathic hydrocarbon what do you think that's made of don't be afraid of the obvious it tells you in its name hydrocarbon contains hydrogen and a carbon it's a long chain of hydrogen and carbon and so this is what we'll see making up the fatty acid tails of phospholipids they're a hydrocarbon and so very brief schematic is that you'd have a chain of carbons and attached to them might be some hydrogen I'm not going to completely flush this out but you can see that so hydrogen hydrocarbon a long chain of carbons with some hydrogen attached and so we'll see this play out in the um membrane here hydrocarbon a chain of carbons with hydrogen on it let's take a look at this word called fluidity fluidity we kind of talked about that already because the membrane is a fluid mosaic model so fluidity as we've already seen just refers to the fact that these phospholipids that make up this membrane they are not stationary there's some flexibility so when we look at the word fluidity of course we could talk about flexible and it is flexible but flexibility could mean different things maybe the membrane bends or is malleable but it also means also that phospholipids can move and when they move they don't just move [Music] move a little bit they can move quite a bit around that summon R again they have to stay in their own layer their own leafl They Don't Really flip back and forth from an inner to an outer leaflet we see them move around in their own leaflet all right let's come in here and talk about some functional things a transmembrane protein transmembrane protein do you think this is specific to one side of the membrane or another or does it go all all the way through the membrane all the way through a transmembrane protein is a protein that spans through the thickness of our membrane so it's going to act like a channel allowing things to go from the ECF to the ICF for example it's called a transmembrane protein now with that we can kind of understand peripheral membrane protein peripheral means it just stays on the outer or inner leaflet it's not something we see a lot of in this class but I just wanted to bring it up because we talk about transmembrane proteins to contrast peripheral membrane proteins are only on one side or the other so they don't go through the membrane they're stuck on the inner or outer leaflet and then putting all this together if a membrane is fluid or if it has the right proteins in place going through that whole membrane we can get all sorts of diffusion to occur we could get simple diffusion we could get facilitated diffusion and that's only if all of these pieces are in place so the diffusion is the movement of solutes with their concentration I'm going to abbreviate here gradient the movement of solutes with their concentration gradient and we will talk about the types of diffusion that exist and which type A Certain molecule may be eligible to use so some molecules can use simple diffusion some cannot use simple diffusion and we'll study why that is so just basic vocab I think it's super important I don't normally go through vocab with people but cell biology is sometimes a confusing intimidating thing and so if we're all starting on the same level with vocabulary then hopefully that helps a little bit any questions before we start going through this a little bit more questions that kind of comeing back to you from like biology 198 principles of biology good old days so we're going to go through the main components I'm sort of set this back up and we're going to look at different parts of our membrane and I'm going in order I'll be moving left to right and in doing so we're going to see information about the most prevalent components to the least most prevalent components to the least so let me start off with sort of a statement here if I can get everything set up that is cell membranes of UK carotic cells are about 50% lipid and about 50% protein about that doesn't mean they're completely 50/50 but this is is about the composition that we'll see so 50% lipids and again that's a fat and 50% protein when we think lipids there's different types we'll find some lipids fats as cholesterol for example but the first type that I want to talk about is something called a phospholipid and there's really two shapes that we find in a cell membrane we'll find fossil bids with completely straight tails like you see on the left and we'll some find some with a kinked or a bent tail like we see on the right and there is a lot of significance and benefit to having that bent tail so that's where we're going to head first is talk about phospholipids we're going to see that phospholipids I'll zoom in on this make it as big as possible without losing resolution phospholipids are just really the fundamental building block of a cell membrane they they provide that I mean they are the most prevalent structure that we'll find in the cell membrane and they really provide the structure the backbone of the entire cell membrane again they are not a solid thing they're not made of like calcium or bone or anything obviously consistency of olive oil but yet they have the ability to provide a lot of structure and the ability to support other compounds that we may find in that membrane let's talk about what we would find in an average phospholipid what we' find in an average phospholipid so we'll see that the phospholipid consist of really two main parts the first is a phosphate containing head see if I can get that to focus a little bit better maybe a phosphate containing hydrophilic head and this is why it's hydropic it has a charge things with the charge like to interact with water so we call them hydrophilic phosphate containing hydrophilic head and so that's kind of the round portion that you see in the drawing above and then also they have two hydrophobic fatty acid tails and these have some interesting features hydrophobic because they don't like water they are long chains of hydrocarbons so we've already defined that and theyve really come in what I call two flavors two structures and that's good we need both of these structures to be present when we think about the structure of a fatty acid tail we're going to first of all see that fatty acid Tails cause our phospholipid we have an outer leaflet and an inner leaflet and it's going to form a by layer in water and that's because the heads like water and the Tails do not you'll see that this phospholipid by layer with its two leaflets forms a stable barrier move this down so people in the back can see it's a stable barrier it's very selectively permeable so once do this down I'm going to go back to the top and sort of sketch out some of these details we've been talking about of our phospholipids I'm going to talk about the value of Kink Tails why it's good that not all of them are super straight why a little bit of messiness in that membrane is actually from a biological perspective pretty helpful all right so I'm going to go back to the top looks like most people are done writing because theyve got a lot of eyeballs so again this is going to be posted so if you don't get it all don't worry you'll have access to it um let's go back and talk about how this pertains to the structures that you have on your piece of paper or your digital device and go from there so I'm going to go back up and I'm going to hit all these points again but put like a little bit of a visual to it so right now these phospholipids are not forming a bylayer there's just one layer of this very simple um schematic right here we would see that their heads are hydrophilic so I'm just going to label some things here hydrophilic and that's because they have a charge they contain a phosphate and phosphate has a little negative charge on it so it interacts well with water so you can think about maybe just a really basic visual this top part here is going to be your polar part or interacts with water and then down here is just a glycerol head and that acts like a really great anchor for our fatty acid tail so you could put sort of the phosphate if you want to put like a little negative charge up here this is a visual that's fine so that's going to interact with water because it has a charge and then down here if you've ever heard the term glycerol head that's the rest of this contains glycerol and glycerol is kind of an evolutionary Marvel in that it allowed sort of the serves as a bridge between something with a charge and something um that might not like that charge so the glycerol head the glycerol would be down here so other parts of this are the fatty acid tails and the fatty acid Tails let me see what color would be good here and also show up fatty acid tails are just long chains of hydrocarbons so here's the fatty acid tail and these really come in two flavors if you'll notice this one these two are rather straight and this one's straight but provides kind of a kink or a Bend from a biochemistry perspective that bend right there is pretty important it comes from a double bond in our hydrocarbon chain that does not want to be straight it wants to sort of kick out or form a little Kink right here like it has a little knee and the benefit of that is it prevents really tight packing of these phospholipids so if all of them had really straight tails they would pack so nice and neat together that it' be really difficult for items to go through this membrane via simple diff Fusion it also be really hard for proteins to be inserted into this membrane if we wanted to upregulate or down regulate proteins that maybe for instance allow glucose into the cell so it turns out that messiness that little Bend there is really helpful for cells that need to get things across the membrane if it wasn't there too tight packing hard to get things across that membrane so we actually like a little bit of messiness in ourselves so again these make up the vast majority of a cell membrane they're not the only game in town but they make up the vast majority of it I hit all of that questions on phospholipids phospholipids move into cholesterol next then and cholesterol is something that we find in cell membranes cholesterol usually you think about cholesterol you're like oh that's bad and they so and so they have high cholesterol but cholesterol in normal limits is really helpful for allowing our cell membranes to function so we're going to talk next about cholesterol so cholesterol has a funky structure which is why I gave it to you I'm not expecting you to just magically sketch that out um so it has a lot of sort of interesting sort of rings shaped structures to it um when we think about where it comes from all the cholesterol you need is actually produced by cells of the liver so you already produce all that you need which is why additional dietary cholesterol maybe maybe not such a good idea but a lot of times people that have high cholesterol you know sometimes we judge them or like oh look at your terrible diet you have high cholesterol don't do that a lot of times it's just genetic their liver just makes a lot of cholesterol and it wouldn't matter if they ate no cholesterol in the diet they could still have high cholesterol what cells in the liver are specifically doing this what's the functional cell of the liver starts with an H so when we say cells of liver Li that's fine but let's give it a name cells of the liver are called somebody said it say louder heyes hepatocytes yeah hepatocytes hepatocytes are the cells of the liver they do a lot like a lot and one of those is produce cholesterol when we think about what cholesterol does what's it needed for it functions to increase the fluidity of the membrane it prevents this membrane from being too stiff too hard to change too hard to put things in or out of so it has a really important function in fluidity increases our ability to make that membrane pliable malleable so it's going to make it more flexible as a unit and flexibility is always a good thing because it gives the cell options membranes need to be flexible otherwise that cell is going to be stuck in sort of this rigid stiff unchanging unwavering container and that is really hard for cells to function in because sometimes they need to change what they get into out of their cell and that's going to require changes to their container the cell membrane so this allows them to do what they need to do it also this sounds like I'm sort of talking it up both sides of my mouth but it also decreases permeability of the membrane making it more selective so we want it to be fluid and Squishy and changeable but we also don't want it to just let anything in and so cholesterol because it's a lipid will repel quite a bit of things so it turns out it serves two purposes keep it fluid but keep it selective so again the ocytes of the liver make all the cholesterol you need in your diet cholesterol reducing drugs a lot of times work on the action of hepatocytes tells them to stop doing that so use a lot of information from here to understand other things that you may have encountered like cholesterol reducing drug all right let me move this around a little bit more we're going to take a look at our next structure glycoproteins glycoproteins and then we'll take a look at proteins here in a moment so before I unmute the screen just take a look at the word glycoprotein glycoprotein what do you think it's made of sugars and protein it literally is a chain of amino acids proteins make up are made of amino acids and it's gonna have carbohydrates attached to it so glyco usually has refers to carb and protein obviously made of amino acids so they have funky little shapes they're not as prevalent obviously as these other things um they are generally found on one side of the leaflet or the other for our purposes they're mostly found on the outer surface of membrane they would be associated with the outer leaflet sort of sticking up into the ECF kind of making the surface of the cell look like a little hairy like kind of it's got some features sticking off of it so it's not perfectly smooth and rarely perfectly round when we think about how it gets its name so we're going to see that the protein core or which is made of amino acids links the structure the glycoprotein structure to the cell so if we were to sort of sketch this in our protein cord would act like a Fastener or like a little velcro helping this stay attached to the cell membrane and cells can change this too hopefully you're starting to realize that everything here is um changeable somewhat negotiable so if I was to draw in just a fosil bilay here just basic two lines we would see that this glycoprotein really kind of sticks out into the ECF kind of waves around in the ECF it's not necessarily rigid so I could sort of color in some ECF and help you understand that there are parts of of the cell that the cell makes that aren't even inside of the cell a lot of it sticks extracellularly so that would be ECF that I just drew and we think about the significance or function of these glycoproteins sticking out into the ECF um we're going to see that the carbohydrates so you got carbohydrates sticking out mostly into that ECF so anchored that structure to the cell membrane mostly with proteins or amino acids and then carbohydrates kind of form a fringe it looks hairy fringy kind of like a caterpillar and that helps in cell signaling so this the the structure of The Fringe is indicative of sort of the function of that of that glycoprotein we want them to have the right structure because they do really important things for example glycoproteins help the body recognize a cell as belonging to your body so you don't attack it it says hey I belong here I'm self SF I'm self cell I belong here don't attack me I'm not a pathogen I'm not an Invader that glycer protein isn't formed correctly the immune system could mistakenly think it's a pathogen and start attacking its own cells what is that the basis of what kind of diseases arve from that heard of autoimmune disease where you start attacking your body cells this is one of many ways that could happen glycoproteins aren't formed correctly immune system doesn't recognize it and it starts saying hey I think that's a pathogen like any other pathogen I'm going to start attacking that soell so we want that Fringe to be um placed carefully and properly so glycoproteins mve to our next um I think one of the more interesting structures probably something that you haven't thought a lot about and that's going to be intracellular proteins as well as those in the membrane so we're take a look at proteins some of those sticking to the outside some of them sticking to the inside but these are going to be proteins and in this particular example since we've already talked about it and defined it these are examples of transmembrane transmembrane proteins and what you'll see here they come in all sorts of different shapes and structures and functions but what you would see is that they are functional allowing things to go from the ECF to the ICF across our phospholipid bilayer so a lot of things that a cell needs like glucose amino acids large amounts of water actually can't get from the ECF to the ICF via simple diffusion so it turns out we need these transmembrane proteins that have a certain structure they have an aquous pore and they allow things to enter a pore maybe they change shape and then they're sort of spit out the other side now that could go the other way I could draw sort of a bir directional Arrow where things from the inside of the cell maybe need to get out so we can see movement either way but they need help getting across that membrane so transmembrane proteins play a big role in cell function so when we think about proteins in the membrane again numerous proteins exist some could be channels or um pores or pumps talk about them in a bit but numerous proteins exist and I just gave you sort of two basic structures here some of these form channels like the one that I drew they have an actual watery or aquous pore that goes all the way through the center and it allows things to move through that aquous pore to get into out of the cell so some form channels that allow continuous movement across that membrane so permit movement across the membrane so picking on the one that I just on if we looked at permitting movement across the membrane what I'm going to do is just draw some dotted lines such that if I could peel off like the front layer of this and we could really look inside of it what we would find in this protein I move this over so my hand doesn't block your writing we would find in here again we're having the ability to peer inside we'd find an aquous pore or channel that is continuous it's got water in it and that water provides a continuous route between the ICF and the ECF and so that's how we get big polar things from one side of that membrane to another so those are channels others though other forms exist other transmembrane proteins May function as [Music] Messengers and when you function as a messenger what you're doing is you're allowing EXT extra cellular signals to create a change inside the cell you're allowing communication to happen between cells so some of our transm proteins are not all about moving things some function as communicators passing information from one cell to another so all sorts of options it really just depends on what the cell needs and we think of options I'm going to end with this statement here for right now proteins in the membrane just like the ones we drew they can increase or decrease a number they're not set nothing about this is set so hopefully one of the take home messages you get from this is that pretty much everything in a cell's membrane can change the location of phospholipids the amount of cholesterol what the glycoproteins look like where they are and what type of transmembrane proteins you have all of this can change so back to my statement that cell membranes are a fluid mosaic hopefully that makes a lot more sense to you now they move around they're pliable and they're really changeable depending on what the cell means if the cell can't change its membrane it's going to have a really hard time surviving because it can't exist in a changing extra saor environment so we want it to be able to have this flexibility so I'm going to give you about five minutes of a break I'll once again negotiate with canvas to show you your quiz score um and at 310 we'll pick it back up say they people [Music] w [Music] [Music] so like the whole thing [Music] I video [Music] [Music] I know I was they were in my room I was like no way me [Music] [Music] I was know I saw that's read okay welcome back 310 I'm going to get right back into it first I think your canvas quiz should be correct you guys able to see your feedback thank you for that so the next thing I'm going to do is show a video about what we just talked about and as I mentioned at the beginning of the semester I can't record this and show a video because YouTube will reject it because it think I'm trying to post copyrighted material so I'm going to pause this the reason that's significant is it's going to stop this video so when I post it at the end of this week you're going to see like today's lecture in part A and Part B because as soon as you push pause it contains that video it closes it does that make sense everybody so this is a YouTube thing I don't like copyrighted material which makes sense being posted by someone else it's called stealing um so anyway I'm going to post this as part A and Part B and that's why so