foreign [Music] this video is going to cover the topics of endocytosis and exocytosis and one of the interesting things about the cell is that it needs to be able to transport certain items into as well as out of the cell and how we're going to do this is through vesicular transport now we're going to have to use a vesicle in vesicular transport so what is a vesicle and it's a membrane-bound Sac that contains some type of particle so for instance with vesicular transport it's different from the other types of transport we've talked about it's different from primary active transport or let's say simple diffusion it's different from active transport because in vesicular transport the cell is needing to move a bunch of stuff at the same time so let's say a whole bunch of okay let's hope this doesn't happen again one two ready one two ready go a whole bunch of let's say protein or um hormones through the cell membrane no no no no no no no no no no no no no no a bunch of proteins and because these are large molecules we're going to need to use a vessel or excuse me a vesicle so like I said one type of the particle may be a protein other things the vesicle can transport would be like very large molecules which we call macromolecules so like a very large uh carbohydrates for instance we can also transport a bunch of water back and forth across the cell membrane through these vesicles now in order to do this vesticular transport there has to be some ATP involved some cellular energy so the main types of vesicular transport would include endocytosis and endome going into the cell and these would include and we'll go over these phagocytosis pinocytosis and receptor-mediated endocytosis and then if we have to transport something out of the cell this is going to be exocytosis so the EXO meaning out all right so let's watch a quick video about each of these processes cells also use energy to transfer materials in bulk but this time by forming membranous sacs that hold their contents Under Wraps in a process called endocytosis part of the surface membrane encloses the material forming a Sac which brings the contents into the cell's interior in the opposite process called exocytosis the sac moves through the cytoplasm to the membrane fuses with it then releases the contents so we go through the process of endocytosis we're going to start talking about phagocytosis and only very specialized cells in the human body actually can do this process of Phagocytosis and these cells would be part of our immune system and so these would be what we would call phagocytes or they're also referred to as macrophage and when we talk about the process of Phagocytosis this actually means cellular eating and that's because and we'll talk about this again phagocytes are bringing in much larger particles all at one time so for instance that macrophagia that phagocyte might be engulfing a bacterium pinocytosis all cells can do this and we call pinocytosis cellular drinking and receptor-mediated endocytosis again all cells can use this and we're going to talk with receptor-mediated there's a special process these cells can go through which is referred to as down regulation so let's start start off talking about phagocytosis and in phagocytosis these macrophage or these phagocytes are going to be using what we refer to as pseudopods and what they do is they're able to engulf okay kind of eat certain large particles on the outside of the cell and bring them into the interior of the cell okay and when we do this we form what's called a vesicle or you can also refer to this as a phagosome because it's happening in a phagocyte all right so in this picture what you can see here is you can see these little pseudopods that are occurring and the pseudopods are now going to engulf this large particle that was on the outside of the cell and bring it into the cell and by way of what we would refer to as a vesicle or that phagosome now imagine what's happening is when this phagocyte comes in contact let's say with a bacteria so you got this little macrophageal this phagocyte zooming around through your body and its job is to be on the lookout for bad guys such as bacteria that get into your system and when the phagocyte sees it it's like oh no got to get rid of this bacteria so what the phagocyte does is it's able to turn on these what we would call kind of water jets so these are located inside the cell and these jets are using ATP energy and the Jets are moving the water or the inter intracellular fluid in the cell and you've got basically two water jets and they're pushing the water like little streams of water from the middle of the cell out towards the cell membrane and these two streams of water are then going to be pushing these two separate areas of the cell membrane so that it looks like these two little arms and that's what pseudopod means pseudo means false pod means arm so these two little arms get pushed outward and it engulfs this bacteria now eventually these two little arms are going to touch and the cell membrane is just going to be able to kind of melt into each other you might say fuse into each other and when it does it pinches off and it forms this vesicle now in that video it showed you that the vesicle kind of looks like a little basketball of cell membrane and what you're seeing here is imagine somebody cut that basketball in half so you could see inside that vesicle so now with phagocytosis again I said that this is used by those macrophage and then there are some white blood cells like neutrophils that can also do this phagocytosis process and you'll see with these white blood cells and if you get onto the internet and I'll show you a video where these phagocytes are able to move by what we call amoeboid Action they look like little amoeba swimming around in the system now in this little GIF here you can see those little pseudopods coming out and then they come together and they pinch off that phagosome or that vesicle and eventually what will happen and we'll talk about this later but you have an organelle inside the cell called a lysosome and it's full of digestive enzymes so that we move that bacteria into that lysosome and we kill off that bacteria using those digestive enzymes and again these little pseudopods are where that cytoplasm or that intracellular fluid is going to flow into okay and that's why we call it also suda because it's just a temporary extension okay so in this picture here you can see the big white blood cell moving like that amoeba and it's chasing through all those red blood cells it's chasing this little bacteria and as it's chasing that bacteria eventually it's going to be able to engulf that bacteria you see how it's changing its body shape those are the little pseudopods that it's producing all right so let's talk about pinocytosis and then receptor-mediated endocytosis so pinocytosis is referred to as being non-selective the reason that we call pinocytosis non-selective is because it's not picky like phagocytosis these are cells that are only going to engulf certain types of items like bacteria or it could even be like pieces of dust that got into your lungs but these large particles that are not supposed to be in the body pinocytosis on the other hand is not picky at all it's not super selective it'll move things like fluids or any type of substance that's dissolved in that fluid now receptor-mediated endocytosis is more selective and we're going to talk about this a little bit more that's because it will only move things that can bind to The receptors or things that can bind to The receptors so that other things can move across the cell membrane all right so pinocytosis if you remember we talked about this as cellular drinking some people also refer to it as fluid phase endocytosis or it can also be referred to as bulk phase endocytosis but we're just going to refer to it as cellular drinking and this is because mainly what's happening now is that the cell membrane is going to fold Inward and as it does it creates like a suction and that's going to pull any fluid in the extracellular surrounding area that is right there where the cell membrane folds in and then all those dissolved solutes along with the fluid are going to move inside the cell so most cells use this method to sample the outside environment they want to know what's going on on the outside of the cell and that's really important because the cell has to be in constant communication with the body so the cell has to know what is going on right outside its front door and we have other things that are happening in the body where it uses pinocytosis like for instance in the small intestine a lot of the nutrients are absorbed through this process of pinocytosis so the membrane component that folds uh Inward and creates that vesicle eventually is going to be recycled back to the cell membrane becomes part of the cell membrane again okay so in this picture it's showing the process of pinocytosis and first of all what you see is the cell membrane begins to fold Inward and as it folds inward it's starting to pull substances into the cell now how that cell membrane starts to fold inward is that in the middle of the cell there are these water jets and now instead of like with phagocytosis where the water jets are streaming from the middle of the cell towards the cell membrane we've got the opposite effect here now these water jets are moving water that intracellular fluid from the cell membrane towards the middle of the cell and so you've got movement on this side and you have movement on this side in the direction of the cell membrane towards the middle of the cell from the cell membrane towards the middle of the cell and that's kind of sucking in or folding in the this cell membrane and it's sucking in sort of like you're sucking on a straw it's sucking in all this fluid and all these dissolved particles in the fluid whatever happens to be floating around gets sucked in and eventually both sides of the cell membrane will touch and they'll fuse with each other and we'll pinch off that vesicle and then we have all those different chemicals on the inside of our cell which is why they referred this kind of as cellular drinking so with receptor-mediated endocytosis it's used for a specific uptake of certain substances required by the cell and we use clathrin coated pits to do this so before we go any further I just want to go through a few details about what receptors are all about remember we talked about Gates that are on the outside of the cell and then on the outside of those Gates we have glycogen and so this entire complex here gate and glycogen together these can be referred to as a receptor okay or if I wanted to draw this quickly I could just draw it like this I could just draw a y and then I would refer to that as a receptor but a receptor is that gate lycogen complex that's on the outside of our cell so to get back to these clathrin pits okay we're using these as one of our roots with this receptor for endocytosis so in this picture you can see that little y shape there this is the receptor and something has bonded to that receptor and when that chemical bonds to that receptor now we know that that chemical wants to get to the inside of the cell so this line right here is supposed to represent the cell membrane now once a chemical has bonded to this receptor Along Comes This protein called clathrin and clathrin is going to bind to the receptor along with our chemical and that's going to stimulate the cell membrane bending inward okay in order for endocytosis to occur like with pinocytosis where you had those water jets now instead of just [Music] um try this again one two three ready go with pinocytosis remember you have those little water jets in the middle of the cell and what those jets are doing is they're moving water from the cell membrane to the interior of the cell and as those water jets are moving the water from the membrane here to the interior of the cell and then again from the membrane here to the interior of the cell you see the cell membrane folding Inward and that whole water jet system is going to be stimulated by these clathrin proteins binding to our receptor and now it's pulling the receptor as well as the vesicle with all of the chemicals into the cell so these chemicals could be things like enzymes or it could be some types of cholesterol which we call LDL or low density lipoproteins iron different hormones like insulin and then we even have viruses like diphtheria or cholera that can move into our cells using this receptor-mediated endocytosis so again this is what you see here this is the cell membrane folding Inward and as it folds inward uh you have all of these receptors along with whatever bonded to the receptor moving inside this vesicle and it's coated with all those clathrin proteins now one of the things that I want you to know about is a process referred to as down regulation so down regulation is a process where the cell decreases the production or the quantity of certain cellular components all right so let's go through this let's talk about this so let's say that we have a cell that is involved in helping us to be able to handle stress and we have several cells like that and this cell is going to help us by producing a hormone called cortisol now the problem is cortisol is really good up to a certain point in helping us to handle stress but if we produce too much cortisol and we produce it too much and for too long of a period of time cortisol can be very detrimental it can hurt the body big time in a number of different ways and we will talk about this in more detail a little bit later on when we talk about the General Adaptation Syndrome so you can look that up in a different video so since high levels of cortisol are really bad for the body the body has to figure out a way to stop this production even though let's say the person is still under lots and lots of stress so the stress hasn't stopped but the body's looking at this cortisol going okay this is not good how can we slow this down so what happens is these receptors okay on the outside of the cell they're constantly being stimulated by chemicals that are telling the cell hey cell make more cortisol we're under tons of stress So eventually what the court what the cell does is it signals those water jets and says look we're overworked we don't want to produce cortisol anymore we need you to do this receptor-mediated down regulation and how we're going to do this is by pulling these receptors into the cell and keeping them on the inside of the cell if there are no receptors on the outside of the cell there's nothing to bind to these receptors and if no chemicals can bind to The receptors there's no signal on the inside of the cell to tell the cell to make cortisol now that can keep those receptors this down regulation can keep those receptors inside the cell for minutes or it could even keep those receptors potentially inside the cell for multiple years until we go through this process of up regulation now up regulation is nothing more than a signal that tells all these receptors that are being kept on the inside of the cell hay it's time to go back out on the outside of the cell and bond with those chemicals again so we can produce more cortisol so basically this is the opposite process to down regulation and we're increasing the quantities of that cortisol inside the cell or whatever the cellular component may be and so with upregulation all those receptors move back outside the cell and we don't exactly know what stimulates upregulation so it can happen at any time now for exocytosis this is the movement of particles out of the cell and again we're going to be using a vesicle that's produced in an organelle inside the cell called the Golgi apparatus and we'll talk more about that a little bit later on so now this is a picture of a vesicle here and you can see all these particles that are being released from this vesicle all right so again if this is our cell and then inside the cell we have some type of vesicle and let's say that our cell needs to take a certain protein I'll put a big p here for protein and we want that protein to be released from our cell so now what we're going to have to do is we're going to have to add this vesicle move to the cell membrane so it's just going to float up towards the cell membrane now once this happens we're going to move to the next step now our vesicle that contains our protein is going to be up at the cell membrane now that this vesicle with our protein is touching the cell membrane exocytosis can occur this is going to show our vesicle now having been fused with the cell membrane and so this is where the vesicle has fused with or become part of the cell membrane and then our protein because now there's a big wide open space our protein is going to be able to be released out of the cell and into the extracellular fluid and this is our process of exocytosis thank you so much for listening to this video on endocytosis and exocytosis