talking about the cell membrane a little tiny bit when we looked at cells in the last unit and you just kind of got a basic understanding that the cell membrane allows things in and out of the cell but we're going to get into some great detail on that when we say cell membrane same thing plasma membrane cell membrane those two are interchangeable so just like something important to point out the cell membrane has some distinct functions one it's a separator it can separate the inside of the cell from the outside of the cell depending on what kind of cell you are if you're a procaryotic cell you're a unicellular organism you're one cell you are separating your plasma membrane may be separating you from the world if you're a cell like in our body it'll be separating you from uh maybe other kinds of cells like you or a lot of cells that are not like you or what we also call the interstitial area which is the space little spaces between cells some things can easily come into cells and out some things need the assistance of a protein to come in and out so we're going to take a look at what are the guards of the different kinds of things in a cell membrane that allows certain things to easily move in and out and What needs assistance through um we'll talk about different kinds of proteins that are embedded in the plasma membrane and then cells do communicate think about your heart cells for example if you put your hand on your chest you can feel the beating of your heart or if you put your hand your fingers on your neck you can feel the flow of blood through your body that's because the cells of your heart are saying everybody contract everybody relax everybody contract and they're doing that in unison so they have to be able to communicate and so there is distinct communication between cells and then there's molecules like hormones um other things within our cells that tell one cell you do this and then it makes that cell do something and then that cell does something and it creates a hormone or some kind of communicator and it flows through the blood it tells something else to do something and we have these chains of events we basically call that metabolism all of the chemical reactions that are happening in our cells and then some cells have to be connected to one another like heart cells not only do they communicate but they're attached so that the cells of the heart are all able to push blood through the heart structure without it leaking everywhere or our digestive system our digestive system has to have tight attachments between all the cells so things like hydrochloric acid that is produced in your stomach doesn't get all over your other organs and dissolve them so we also have attachments and then as I mentioned before that some cells are going to be producing outcomes that tell they produce something and it tells another cell to do something and then that makes that cell do something tells another cell to do something we have these chains of reactions that cells are responsible for regulating what happens within a cell or within an entire organism so those are the main functions a lot of important functions in the cell membrane that's why we spend a whole chapter talking about just this one specific organ out okay so let's talk about some of the characteristics there's this term permeable what that means is that the cell membrane allows some things in easily keeps some things out tells some things you can come in you got to have help so that's permeability allows some things in and out of the cells the components of the cell membrin the main components are a phospholipid bilayer there's the word lipid in there so lipids are a really important part of our cell membrane but also there are many different kinds of proteins scattered throughout that phospholipid bilayer there's other things that are embedded in the phol liid bilayer in addition to proteins like cholesterol for example it's a stabilizer of our cell membranes that's why we track cholesterol as part of our health because you want cholesterol but you don't want too much but you also don't want too little and so we look at what's in the cell membrane we'll take a look at other things as well the cell membrane sets up concentration gradients for different kinds of compounds molecules that's what you had done there with the dialysis tubing you set up a concentration of different percentages of sugar or syrup in those two different sausages that you made there's syrup inside of those but not outside in the water you place them in and that's what we mean by a concentration gradient is that you've got a concentration of something on one side of a cell but not on the other and then something happens when you have that situation we'll take a look at that when we get into lab and we call the cell membrane a fluid mosaic model the term Mosaic when we're thinking about art means like a bunch of different pieces that make a bigger piece of art and so what we mean by this in terms of a mosaic model is there's a lot of different kinds of things embedded in the phospholipid Bay but also it's fluid and so here's another one of those trippy Concepts like water with hydrogen bonding makes very strong bonds which makes our body of approximately 75% water feel more solid it's the same thing with our cell membranes is that our cell membranes have polarity issues as well that make our cell membranes even though they're liquid right it seems like we're more solid so again another contributor to making us have structure but still have some flexibility in that structure by actually being liquid but feeling more like a solid so we're going to talk about all the different features and how this all comes together making the cell membrane function and its characteristics so first thing we're going to take a look at the phospholipid bilayer these are the lipids that are found in the cell membrane they're the predominant fat in our cell m braines so if you remember last two chapters ago chapter 3 we talked about biomolecules and we took a look at a type of fat that was a glycerol backbone had a glycerol backbone and then Three fatty acid Tails when we're taking a look at the phospholipid by layer what we see with the lipids that make the majority of the lipids in the cell membrane is what we took a look at was that we had a glycerol backbone and three Tails which would give the structure like this glycerol backbone one two three Tails uh when we're taking a look at the phospholipid bilay it has two tails instead of three and the way that they configure is they configure like this so that when we're taking a look when we're taking a look at the structure of the cell membrane is that we have a situation where you have these fatty acids are packed closely together and they make here this is the outside and this is the inside of the cell what they do is they set up a barrier system to divide have a distinct division between the outside of the cell and the inside of the cell and what makes them just configure that way it's all about polarity that just like water has a polar a positive slightly positive polar side slightly negative polar side same thing here is that you've got positive you've got positive and negative sides to that so that the negative sides come inside and the positive sides go on the outside and so they just configure that way we talked about polarity before so which of these was something that we know has polarity and is really really important to our cells water yeah water okay so the reason that they configure this way also is because there's a lot of water here and there's a lot of water here and so the heads face toward water because the heads are hydrophilic which means they like water and the tail tails are hydrophobic so the Tails face each other because they're like let's stay away from the water outside and inside of the cell we know that fats are in general hydrophobic right they stay away from water and we can see that they have this hydrophobic region because the water doesn't mix together with water the oil doesn't mix together with water excuse me so the Tails especially stay away because those two tail regions are hydrophobic it doesn't allow the fats to mix well with water it also means that you can't dissolve you could even put this right you can put this in a blender and it'll mix it together temporarily and you think like oh it's pretty uniform and then what happens you let it sit and the fats start to go to the surface and try and get away from the water hydrophilic the term hydrophilic this part philic means attracted to water if you're like well how do I tell the difference between hydrophobic and hydrophilic I think we all know if you have a phobia of something you don't like it right you repel that thing you try and stay away from it so then hydrophilic is the opposite sugar is hydrophilic sugar it can you can take it and you can mix a spoonful of sugar into water and it'll evenly distribute throughout the water it's hydrophilic it's a substance that easily or readily dissolves in water okay and then here's just a nicer um diagram of the plasma membrane the phospholipid Bayer you can see the heads are on the outside side the heads are hydrophilic because they face the cytoplasm which is a watery environment so they're attracted to that heads on the outside there's water water water all over our body so even in the extracellular spaces or what we call interstitial areas there's water so the heads face the water areas and make this hydrophobic or waterfree area inside all right so now we're going to take that phospholipid Bayer we're going to start to plug in some proteins throughout and this is what we call the Mosaic of proteins because we have so many things that come in and out of our cells we have to have so many different kinds of proteins that are also embedded in that phospholipid Bay so the proteins are mainly responsible for moving things in and out of the cells they are for communication they're the ways that cells communicate with one another they can identify is this the same kind of cell as me like are you also a heart cell are you also a homo sapien cell like one of the same species are you a bacterial cell and should I notify our immune system to attack you and get rid of you all right so a little reflection where will the hydrophobic parts of a protein be located in terms of the phospholipid Bayer will they be on the outsides of the phospholipid Bayer or will they be on the insides good okay so if a protein has a hydrophobic no oh yeah it's it's hydrophilic Hydro sorry I said hydrophobic and then I yeah sorry on the inside so you guys responded right to me hydrophilic parts will be with the outside hydrophobic will be on the inside sorry I read that wrong so you were correct in what I said this is a different question hydrophilic outside hydrophobic inside thank you okay so any hydrophilic regions of a protein will face outward if there are hydrophobic regions of a protein they'll be in the Middle with the Tails because compounds are so large there will be hydrophobic and hydrophilic and hydrophobic and hydrophilic areas there'll be a lot of different areas because these molecules are quite large let's explore the five different major kinds of proteins certainly there are more than that but we're going to take a look at each of these and then talk about their function and how that relates to also the overall function of the plasma membrane so first one let's talk about transport proteins if something does transport what does it do it moves thing yeah good so these are going to be responsible for the movement and specifically of hydrophilic molecules across the membrane they're facing on the outside of the cell and on the inside on the edges of the plasma membrane there are two different kinds two major kinds channel proteins and carrier proteins these go from simple to more complex in their function let's take a look at the channel proteins oh here we go question now I'll try and read it correctly this time do transport proteins move Mo molecules that are attracted to or repelled by water attracted to good okay attracted to yes because they're hydrophilic they're attracted to water and I I did it right this time okay so a channel protein it has a Channel or a pore it can move stuff through that Channel or pore that is embedded in the phospholipid Bayer based on polarity and size there are different kinds of channel proteins so one will be for like the negative chloride ion one will be for the positive pottassium ion so we don't have just one kind you have many kinds that are the size of their Channel or Poe is based on the size of the molecule that they are transporting across so we do have some specificity even Within These major categories so for example here we've got a chloride ion panel protein the size of this is going to the size of the channel is going to perfectly fit the chloride ion if we have let's say another one for the hydrogen ion hydrogen ions are very small if we remember hydrogen is a very small atom or element it's our smallest one so the size of the protein as well as the channel is going to be smaller because it's only going to fit that particular one and um even though this fits chloride in its bigger things that are smaller any atoms or ions because they're smaller they will not be able to go either so there is a little specificity on that too I know this looks really really simple but just to know they are very specific to what they move across and even if you're smaller you can't go into one of the bigger channels if you take a biochemistry class you'll probably look at that in more detail or a Cell Biology class you'll find out more details of why and how all right so let's talk about carrier proteins when you carry something you have to grab it to carry it across so a carrier protein actually has to grab on to the molecule ion that it carries across the protein so there is some kind of interaction between the carrier protein and the molecule that it is transporting these protein channels say closed until the molecule that they're transporting comes along and then it grabs onto it which stimulates the channel to open up and then push that molecule through but for the most part it closes up the channel and until something comes along so if this is the inside of the cell and this is the outside it'll be like this and then when something bumps into it that is specific for that kind of carrier it goes like this and it grabs onto it and then it pushes it through and it goes back to being closed closed this is what I mean by it changes its shape so if it's like this and it's closed up and that molecule comes and bumps here it grabs onto it and then the channel goes from being closed to open pushes that through and then goes back to being closed so it temporarily is doing this that's what we mean by changing shape yes so these are also yes yes they are also uh all the five different types are scattered throughout the phospholipid bilayer and then even you can see within the types like these two transport proteins not only are there two different kinds but within the kinds there are more different kinds yeah good question so a lot of times what happens is that they will exchange one molecule for another this is the way that our muscles contract is that within a protein they'll actually do this and they will flip this from the inside with that for the outside so they do like a trading thing so they get very very very specific sometimes they're just like one thing that they push through and sometimes it's two things that they exchange for one another so here you can see and what we mean again by change in shape you can see in your illustration that the channel is closed when a molecule that specifically fits into that protein this protein is specific to only passing this green molecule through when this binds into the edge of the protein it stimulates that protein to go from closed to open pushes that through once that's through goes back to being en closed all right there's also our second class which are receptor proteins receptor proteins do essentially the same thing the receptor protein is going to be closed something that it it is specifically going to interact with hits that it binds it and not just in some cases it will pass that through in some cases just The Binding of that one thing will cause a reaction and cause the cell to undergo something really really big and important so receptor proteins are similar to a carrier except for carriers just exchange like little stuff receptors are responsible for really big cellular events like a hormone for example might bind here and when a hormone like estrogen or testosterone binds to to a specific receptor in some of our gonads or our organs that are responsible for sexual function and development that at a certain point in our life at around you know between 10 and 14 our bodies undergo puberty and so if you're a biological female you start to produce extra or massive amounts of estrogen if you're biological male you start to produce massive amounts of testosterone and when estrogen or or t the estrogen or testosterone bind in our gonads it stimulates those gonads to do all kinds of stuff to start a series of reactions that we call puberty and that's a big life event it takes like you know between maybe uh four years and eight years for us to fully undergo puberty because part of puberty is also growing right and so by the time you're 18 maybe you've stopped growing maybe um like for female your period has become regular for males your voice has completely changed by then you have a lot of muscles um so that's like what the receptors would do is something really really big for the cell or the organism another example is that when a cell is starting to break down it gets stimulated to replace itself with a new cell and so that whole process of cell reproduction the receptor proteins are responsible for something really big that's happening to the cell so here for example you have some kind of of big messenger molecule like for maybe it's a hormone binds into the receptor protein and then it just causes a lot of things to start happening like big big big events enzymes enzymes are really important for every well maybe not every but almost all of our chemical reactions in our cells enzymes are going to help to speed up our chemical reactions and also save us energy in the process so they do this facilitation of a chemical reaction and by them being a facilitator they cause us less energy to be spent so for example let's say you're having a birthday soon and you don't have a ton of money and so you are going to plan this really fun birthday party and you've got all these details tells that you want to happen at your birthday party is it going to take you a lot of energy to make it all happen yourself right okay so an enzyme would be like hiring someone a party planner you pay them money and then they do it all for you and you show up and you're like oh this is great I don't have to do anything right so the party planner saves you all that energy that's like what an enzy on does is there a facilitator of chemical reactions they help them to go faster and smoother and lowers the amount of energy that cell needs there most uh sorry many are located in the cytoplasm many are located in the cell membrane some of them are just attached to the edges of the cell membrane so they have different places where you can find them as well they're kind of found anywhere a chemical reaction might occur we'll talk a lot more we actually the next chapter will all about enzymes and um specifics about them because they're so important all right recognition proteins recognition proteins are found on the edges of a cell when you looked at the cells under the microscope last week or earlier this week and last week um it kind of looked like the cell membranes and the cell walls were flat if you take a look at them underneath a really strong microscope like an electron microscope what you would see was that you would see details of those membranes and in those membranes you could see look at all these things that are sticking off they kind of look like a tennis ball a lot of fuzzy things sticking off all of those different things are recognition proteins they're kind of like the wallet of a cell these will say I am a homo sapiens cell so that our bodies can tell the difference when a bacterial cell comes in if it doesn't have a particular fuzzy thing on it a recognition protein then we flag it and we say and that flag notifies our white blood cells or our immune system like you need to destroy this thing because it is not one of us the fuzzy things will also say things like I'm a blood cell I'm an a blood cell I'm an A plus blood cell so you could have a lot of different information about the cell what it does what can bind to it all on the surface there so we have a lot of important information on those recognition proteins that tell so much about what the cell is and what the cell does and how it does it and who it can interact with and what atoms or molecules can't interact with and so it's very very specific we often call them glycoprotein attachment sites and as I mentioned very these are very very very critical in the way that our immune system monitors what's in our body the white blood cells are constantly doing this like bump yep homo sapian yep Homo Sapien yep Homo Sapien wait nope this is a staffle cacus orius this is not something we want in our body let's flag this with antibodies and let's target it for Destruction and those flags tell somebody else in the immune system hey you come over here and get this and then we have connection proteins and this is how our cell membranes are held together they serve as anchor points we have a bunch of different major kinds and we'll talk a little bit more about these at the end of this chapter but as I mentioned yeah are attachment that the same um it's like yes they are the same thing so if you want to yeah write connection with attachment um it probably is the new we have a new book we're using so they probably just call it one thing verus the other so maybe write down connection also thank you for bringing out thank you and then just to mention cholesterol cholesterol helps to stabilize our cell membranes we do want cholesterol in our body there's some that's better than others like plant cholesterol for the most part is better than animal cholesterol helps also to facilitate all of those proteins to allow what comes in and out to be monitored and regulated so when we talk about a mosaic of proteins this is what our cell membranes more so look like is that we have a lot of different kinds of proteins that connect to a lot of different things some of those proteins are connected to the cytoskeleton some of them are connected directly to some of the organel that you studied in the last chapter some of them are connected to other cells and we also have little notifiers like this those glycoprotein attachment sites for recognizing what kind of cell we have so lots going on within the cell membrane so the blank portion of the cell membrane is responsible for the isolating function of the membrane while the blank portion regulates exchange and communication with the environment so what two major groups are we talk about and then which applies to which group all right what do you think which number so the lipids the lipids are the oltion the lipids will essentially block most things up the proteins all those different kinds of proteins are going to help get things in and out of the cell communicate regulate and be Messengers