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Video transcript

let's talk a little bit about exocytosis which is how the cell is able to release larger molecules that might be used by the rest of the body other cells or maybe it's going to be part of the extracellular matrix and to understand how this works is really the reverse of endocytosis we're going to go and produce some proteins in the endoplasmic reticulum this is our classic example those proteins are then going to bud off in their own little vesicles which then merge with the Golgi apparatus where they are further processed so they're processed in the Golgi apparatus right over here and then eventually they're going to bud off of the Golgi apparatus in new vesicles and those vesicles are going to make their way over to the cell's outer membrane the plasma membrane and the the membranes of the vesicles are going to merge with the membrane of the cell and in doing so they're going to release their contents and this is classic EXO tight cytosis there are other cases where maybe it releases it merges partially releases the contents and then buds back it's called the kiss and run method of exocytosis but the classic one is it merges with the membrane we can look at this this membrane after it hit after the vesicles membrane has merged with the with the plasma membrane the membrane might look like this it might look like this of the vesicle let me do the vesicles membrane and orange if the vesicles membrane is that in orange well now it has merged like this and it has released its contents it has released the protein 2 to be used someplace else someplace else in the body and I want to be clear this membrane and I talked about it many times in many other videos even though I've drawn it as one line right over here this is going to be this is going to be a phospholipid bilayer so if we were to zoom in if we were to zoom in it would look like this it's a phospholipid bilayer so these are some of the phospholipids that were part of the original a part of the original membrane and then we also in my little box I get some of the ones that are part of or that were part of the vesicle that was holding that protein that were part of the vesicle that was holding the protein so I really want to stress I want to really stress these lines and right these are by layers of phospholipids and all of the these lines these membranes that you see these are all by layers of phospholipids just to make sure just to make sure that we are visualizing this correct and that's what exocytosis is and one thing that I find interesting is when you first learn about it you see a diagram like this and you just assume okay well these bubbles of these you know with these membranes they just you know randomly must float eventually to the membrane and where they get merged and then they release their their contents but it actually isn't that chaotic they actually can sit on tracks so they actually can sit on tracks remember we talked about the cytoskeleton which isn't drawn enough probably because it makes drawings really messy but whenever we think about a cell there's all the structure to it there's all this structure to it microtubules microfilaments intermediate filaments all of these things over here that not only provide structure to cell but they can be used to transport and these vesicles these vesicles can actually ride can actually ride on these structures and you could actually have motor proton motor not protons motor proteins that are using ATP to actively push the vesicle containing its contents so this is kind of a transportation it's it's really like a factory to push them towards the membrane so that they can be released so whenever I think about it's fascinating because I always talk about these cells being a universe unto themselves and they aren't just these blobs they have all of these structures there's all of these proteins that are really an unbelievably small scale able to do these fairly intricate processes so what I just showed you at once again this is classic exocytosis you'll see it when you have proteins lipids being produced by the cell that need to be released somehow they're also famously used in in neurons at when they want it when you want the chemical signal when you go from one neuron to another you have exocytosis of nerve of neurotransmitters that will trigger the next neuron so these are very very important processes our bodies would not function properly if we or wouldn't function at all if we did not have exocytosis
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