Golgi Apparatus Structure & Function

Golgi Apparatus Structure & Function Transcribed by TurboScribe.ai. Go Unlimited to remove this message. What's up Ninja Nerds? In this video today we're going to be talking about the Golgi apparatus. We'll go over its structure and function. Before we get started, if you guys like this video, it m...

Golgi Apparatus Structure & Function Transcribed by TurboScribe.ai. Go Unlimited to remove this message. What's up Ninja Nerds? In this video today we're going to be talking about the Golgi apparatus. We'll go over its structure and function. Before we get started, if you guys like this video, it makes sense, it helps you, please, please support us. And one of the best ways that you guys can do that is by hitting that like button, commenting down in the comment section, and please subscribe. It really, really helps us out and we really appreciate it. It shows us some love. It just helps us to continue to keep making these videos free for all of you guys' enjoyment. Also, if you want some notes, illustrations to follow along with me, go down in the description box below and take you to our website where you guys can check all that stuff out. But Golgi apparatus, what is the structure? So it's a really cool structure. It's one of the organelles inside of the cell. So at this point, we've obviously talked about the nucleus. We've talked about the endoplasmic reticulum. Those are all organelles. The Golgi apparatus is a really cool organelle. Now, when we talk about this, I like to think about a structure as though it's kind of like this folded membrane, right? So it's this kind of like folded membrane, if you will. And there's a couple different anatomic or structural points that you need to know. So here we have the nucleus, right? So here's going to be the nucleus. We already talked about this in great detail. Here we have our rough endoplasmic reticulum. We talked about that in great detail. And here you're going to have the Golgi apparatus. So again, it does have this kind of like convoluted or kind of like coiled membrane, if you will. And again, it's a phospholipid bilayer around that. But one of the big things is on one edge. So the edge facing the rough endoplasmic reticulum is a very specific size. So this is called the cis Golgi. So the cis Golgi is the part of the Golgi which is near the rough endoplasmic reticulum. The basic concept behind this that we'll talk about a little bit later is that whenever the rough endoplasmic reticulum is done modifying and synthesizing particular proteins, what it'll do is it'll bud off a little vesicle that contains its particular proteins that have been modified in a particular way to go to the Golgi. And it goes on the cis side of the Golgi. And I told you that one of the ways to be able to remember that it's destined to go to the Golgi is that we put specific types of proteins on its surface that really kind of says, hey buddy, it's time for you to specifically go to the Golgi on the side. You guys remember what that protein was called? Here, these are called your COP2 proteins. And they're really helpful in being able to send this vesicle from the rough ER to the Golgi. So that's one side of the Golgi, the cis Golgi. Then you have obviously inside of the Golgi, the lumen. That's where some of the reactions are going to take place that we'll talk about in a little bit. But on the other side of the Golgi, this side that is going to be facing towards the cell membrane. So here's your cell membrane here. This is called the trans Golgi. And the trans Golgi, I just want you to think about in two ways. One is after all the modifications occur inside of the Golgi to that protein, what it does is it does something really cool where it'll bud off the modified protein in a particular way where it's then sent to either go to the cell membrane. And from here, it can be excreted or become a part of the membrane. Or it can also do something else where it turns into, we'll give it a different color so we understand it's a different thing. It can get turned into lysosomes. So that's the other aspect of the Golgi. And again, inside it, it'll have this protein that will undergo a bunch of different types of modifications. So that's really kind of when you talk about the Golgi, the basic structure of it is there's this convex. Let's actually write that down as well. The convex side, also known as the cis Golgi, also known as the side of the Golgi facing the rough endoplasmic reticulum. Or the trans Golgi, this is the concave side. This is the concave side, also known as the trans Golgi, also known as the Golgi that faces the cell membrane or those lysosomes that it's nearby. All right. So before we move on and start talking about the function of the Golgi apparatus, I want you guys to watch a quick little animated video by our friends, Nucleus Medical Media. They got a really awesome video that will give you a quick little recap, but in a cool animated way. Check that out and then we'll talk about the function of the Golgi apparatus in more detail. Proteins and other materials emerge from the endoplasmic reticulum in small vesicles where the Golgi apparatus, sometimes called the Golgi body, receives them. As proteins move through the Golgi body, they're customized into forms that the cell can use. The Golgi body does this by folding the proteins into usable shapes or adding other materials onto them, such as lipids or carbohydrates. You will see an organelle called a lysosome. Lysosomes are the garbage collectors that take in damaged or worn out cell parts. They are filled with enzymes that break down the cellular debris. All right, so we're back now. So one of the big things that I want you guys to understand is Golgi apparatus, with the function of it, it's a really cool structure. And we have a little bit of an idea here that it has three particular types of functions. One of the biggest functions is it modifies proteins, right? So it sieves those vesicles. We already kind of talked about this a little bit. To recap it again, because it's always good for repetition, inside of the nucleus is your DNA. DNA can get transcribed into something called mRNA. mRNA can then leave these vesicles and then bind onto all these ribosomes that are placed on the rough endoplasmic reticulum. And then from here, it'll then do what? What we know is it can get translated. And when it gets translated, it synthesizes some specific molecules like proteins, which are going to draw with these like globs here. These are my proteins. Now, what happens is the proteins go through a particular process in the rough ER that we already talked about called N-linked glycosylation. So they'll run through the rough ER. And then after they run through the rough ER, we'll just quickly recap here. What did they have? What happened here in the rough ER again? Well, when it's going through the rough ER, we said that they add on a sugar residue, an oligosaccharide. And they add it on to, if you guys remember, they added on to asparagine. That's why we call it the N-linked glycosylation. So if you guys remember, just as a quick recap, in the rough endoplasmic reticulum, the particular reaction that took place was what's called N-linked glycosylation. Now, some of you might be wondering, why do we call it N-linked? Really, really quickly. All it is, is you take this blue color here, this blue color here. This is a sugar molecule. Here's your sugar molecule. You're going to add it on to a protein. But on this protein, there's a specific amino acid. And this amino acid here, which we're going to kind of show like this, is called asparagine. And asparagine, when it kind of connects or clicks with this sugar molecule, really asparagine has a amino group on it. And there's the N that's linked to our sugar residue. That's why we call it N-linked glycosylation. But protein's been synthesized at the rough ER, modified a little bit in the rough ER via N-linked glycosylation, and then packaged into a vesicle. And then once it's packaged into this vesicle, it says, all right, baby, let's send you on to the next point here. And the next thing I'm going to do is I'm going to send you over to the Golgi. Do you guys remember which part of the Golgi faced the rough endoplasmic reticulum? It was the cis Golgi or the convex side of the Golgi. And in it, it's got this protein that's undergone some small modifications. Do you guys also remember what was the protein on the surface of the vesicle that determined its transport to the Golgi? It was the COP2, COP2 protein. And that will determine its direction of saying, hey, you need to go to the Golgi. And then what it'll do is it'll fuse with the actual membrane of the Golgi because they're both phospholipids and lipid will dissolve in lipid. We know that. So when it fuses here, it'll fuse with this Golgi membrane and then release its contents, which is this glycoprotein, where? Right into the Golgi apparatus. And then there she goes to get further modified. Now, really quickly, before we go on and talk about the Golgi does, there's a reason I mentioned this COP2 protein. So COP2 protein allows for one direction, this direction from rough ER to the Golgi. Well, there's probably a COP1 protein in there. Yeah. You know, it's funny. Sometimes if I want certain proteins from the Golgi to go back to the rough ER for whatever reason, maybe more modification processes need to occur, whatever it may need to happen. Sometimes the Golgi will bud off particular molecules here. It'll bud off little vesicles and these vesicles will then actually contain some specific protein in them that they want to send back to the rough endoplasmic reticulum. So if I want to send back a protein to the rough endoplasmic reticulum, maybe for some particular reason to get modified further, who knows? I could actually bud these off. And if they go in this particular fashion where let's say that they move from Golgi to Golgi all the way from the trans side to the cis side. And then from here, it buds off and then tries to move its way backward towards the rough endoplasmic reticulum where it can then actually do what? Maybe it fuses and releases its contents back in. This is another particular protein that has to regulate this. Do you guys know what this protein is that actually is on the outer surface that determines it going backwards from the trans Golgi to the cis Golgi to the rough ER? Do you guys know what that is? This protein on the surface is called COP1. This is called COP1. So what I want you to know is COP1 allows for the transport of vesicles containing glycoproteins from the trans Golgi to the cis Golgi to the rough endoplasmic reticulum. COP2 controls the movement of the glycoprotein from the rough ER to the cis Golgi. That's what I want you guys to understand. Okay, cool. Next thing is we got the vesicle via moving anterograde. Anterograde will be COP2. Retrograde will be COP1. Now, once this is continuing to move anterograde towards the end direction, which is cell membrane, lysosomes, that's the whole point. Once it gets into this part here, so we're going to release from this vesicle our glycoprotein. Once it's released, time for it to undergo some specific processes. So there's a couple different things that these enzymes that are present inside the Golgi will do. You know what they'll do? They'll do a bunch of different modifications, believe it or not. So it's going to run through this like a football player in practice and undergo a bunch of different modifications. And by the time it's completely modified, what it's going to have at the end of it now is the fully packaged modified protein that now has a very specific destination for it. So, okay, now here's my protein and maybe I've modified it a little bit more. Here's my protein and then on it, let's just say I have, here's a little bit of different, I got all these different things that are added onto it. What are the reactions that occur here in the Golgi that are a little bit different? Let's write these down. The first thing is I take this protein, right? And let's say here, I've already had this process occur. I've already had, let's say here, I have my N-link glycosylation. So this is already occurred in the rough ER. Once it goes to the Golgi, it can then do three particular things. I can trim a little bit of this. I can trim the sugar residues off of this N-link glycosylation. So that's one thing I can do. So let's write that down. First thing I could do is I could trim the N-linked glycosylation. And that might just like make the protein a little bit more specific to be activated. So now if I were to have this protein, maybe instead of it actually having all of these things here, it's just going to have a shorter sugar residue. And that might be enough to activate this particular protein. So now all I did was I just trimmed it a little bit. And now in this state, maybe it's active. This is an active protein that's ready to be released or incorporated into the membrane or become a part of lysosomal enzymes. The second thing I could do, so that's one thing I could do. One thing I could do is I could trim it. The second thing I could do is I could add another sugar residue, but not to an amine group. I could add it to a hydroxy group, the oxygen group. And so if I do that, we actually call since N-linked was I was adding a sugar to the amine group of an amino acid. Well, O-linked glycosylation, which only occurs in the Golgi would be adding a sugar residue onto what? Onto the hydroxy group here of an amino acid. So you see, notice how there's no kind of sugar residue. Now, if I draw this one here, look at this puppy here. So now I got this next one here. This has gotten an amine group. Here's, I got an NH2 group, and maybe it has again, some type of residue here, but now off of this, I want to add a sugar residue onto this one. So now I have a sugar residue on the hydroxy group of two particular amino acids. You don't have to go crazy, but the two amino acids here that it can add onto and make this one active that you could add on here is one is called serine is a type of amino acid with that hydroxy group. And the other one is called threonine. For the amine group, this one here is called, we're going to abbreviate it asparagine. Okay. So these are two of the mechanisms so far. One is I could trim the sugar on the N-linked glycosylation, add a sugar to the hydroxy carbon, O, the oxygen molecule of the protein, the glycoprotein. And the third thing I can do, which is really important, is I could do what's called phosphorylation. So this is the last particular reaction here. Phosphorylation. And all that happens here is you phosphorylate a on this, there's a sugar residue. Let's just say on that one of the sugars I'm going to put is mannose. So maybe on this one, there's a little mannose sugar. Maybe on this one, there's a little mannose sugar, same kind of concepts. I'm going to add a phosphate onto the mannose. And when I do that, the end result should be very, very important here. Carboxy group, amine group. Here you have your NH2 group. Here you have your hydroxy group. Let's say that there's a sugar molecule on either one of these. Doesn't really matter. Sugar molecule here, sugar molecule here. But the big difference here is that there is a mannose sugar here and a mannose sugar here on that sugar residue. Okay. If I were to put a phosphate on these, it activates them very, very specifically. So I put a phosphate group onto this. And when I phosphorylate the mannose of the sugar residues on the glycoprotein, it activates it and makes it only distestant for one particular point. This is active and it will only be active for lysosomes. It'll only, these proteins will only go to become lysosomes. Super important. So this is the protein modification. One is I can trim it, the sugar on the N-linked component. One is I can add a sugar on the oxygen of serine threonine. The third thing is I could phosphorylate mannose on the sugar residues and make it only particular where these proteins only become a part of the proteins of lysosomes. So now all this is occurring in here. What types of things again? Trim. Trimming is one mechanism. Second is O-linked glycosylation. And then the most important one is phosphorylation. Phosphorylation. And this phosphorylation is specifically for mannose. And this will allow for the stimulation of lysosomal enzymes only. That is key. Okay. So now whenever all these modifications occur, maybe I add a little sugar residues on there on different points, right? Or maybe I add a phosphate group somewhere on that mannose sugar. All these different things have occurred. After it's done, it's then said, okay, well, I've done what I need to do. What I'm going to do is I'm destined for three particular things. One is if I don't have a mannose that's phosphorylated, then I have glycoproteins that have been completely activated in a very specific way. And they're ready, whether it be trimming, whether it be N-linked glycosylation, O-linked glycosylation, they're done. From here, we can do two things with these. One is I could fuse them with the cell membrane. Second thing is they could fuse with the cell membrane and be excreted. They could be excreted. Right? We've already talked about this a couple of times. So now this could actually be excreted out of the cell, or it could become what else? Lysosomes. And the only way that we know that you'll make lysosomal enzymes is you have the glycoprotein undergo a very specific type of reaction. It'll have the N-linked glycosylation. It'll have the O-linked glycosylation. But on that sugar residue, there's one specific sugar called mannose, which I have to phosphorylate. And this will become lysosomes. So the destination, the Golgi says, I know where you need to go. I'm going to send you to become a part of the membrane. I'm going to send you to be excreted, or I'm going to send you to become lysosomes. That's another function, a really cool function of the Golgi apparatus. And so from here, it can actually determine the three destinations. One is it can say, I'm going to package you to go to the lysosomes. So now these vesicles, when they bud off, this is now a lysosome. Or I can send you to become a part of the, become a membrane protein. So maybe this glycoprotein is going to be a channel protein. Maybe it's going to be an ion. Maybe it's going to be a carrier. Who knows what the heck it's going to be. Or the third thing is it can be excreted via exocytosis. So these are the three particular things that can happen from the Golgi. So the Golgi receives proteins, glycoproteins, modifies them in these three particular ways, and then determines their destination. Because you know what's really cool is when it modifies it in a particular way, it modifies it to where it gives this thing a specific signal sequence. So these have like a specific signal sequence. So it's kind of like a little like a, like an Amazon thing. Like when you go to Amazon, they have to package particular things and determine where they're going to go. They put a little tag on these proteins, these glycoproteins that says, hey, here's where you need to go. And then it'll help to guide them towards these particular locations. So if I want this to go to the cell membrane, I can actually use specific proteins. Let's represent this one with, let's do it here with pink. Why not? I can put little proteins on this that coat these and make sure that they're destined to go towards the cell membrane to either be excreted or to also be again, a part of the cell membrane. And these proteins typically tend to be clathrins. So clathrin proteins. Okay. And they'll coat these vesicles and say, hey, you need to go to the cell membrane to either be released or to fuse with the cell membrane. The last particular mechanism of the Golgi apparatus is it can recycle proteins. So let's say on the cell membrane here, I have a particular protein that it's done its job. It's completely finished its life cycle and says, hey, you're done, buddy. What I want you to do is, so let's say it's this protein, let's say this, let's say that the Golgi manufactured this particular protein right here and it did its job. So it helped to be able to modify it, determine its destination, incorporates into the cell membrane. Over time, over time, the protein becomes old. It's time for it to actually be, eh, we're going to kind of fix you up a little bit, take you back in. What it'll do is it'll invaginate this puppy and it'll actually bring this in into a little thing called an endosome. And then what will happen is this endosome may get kind of broken down by lysosomes. And whenever it gets broken down, what it may do is it may release these proteins back into the Golgi to be further modified, repackaged, and sent back out to go back to the cell membrane. So that's another particular function of the Golgi apparatus. So again, recapping the functions of the Golgi. First thing is it's involved in protein modification. Receives proteins from who? The rough ER. Going to which side? The cis Golgi. How does it know to go there? COP2. If there's proteins that are determining it to go back to the rough ER for maybe further modifications, how does it know to go back there? From trans to cis to rough ER. COP1 is the protein on the vesicle that determines its destination. If it goes to the Golgi, protein gets released into the Golgi, the Golgi modifies it by which ways? Cuts some of the sugar off of the N-linked point of the amino acid asparagine, or adds some sugar residues on the hydroxyl or the oxygen group of an amino acid. Or what else does it do? It maybe takes the sugar residues that you have here and finds one specific sugar, mannose, and adds a phosphate group onto it. Phosphorylation reactions. Once it does that, that's the three ways that we will activate the proteins and then determine their destination. Once we've done this, we can then say, okay, I can send these to become lysosomes, membrane proteins, or be excreted. If I coat them with clathrins, they're usually destined for the membrane or to be excreted. If it has this mannose 6-phosphate on it, it's destined to be a lysosome. And the last thing is for proteins that are maybe worn down and need to undergo recycling, we need to fix them up a little bit. We can bring them in and the endocytosis, this process here going from here to here is a endocytosis. And we'll make this thing called a endosome. And endosomes, technically, they get broken down a little bit by something called a lysosome, which you already knew. Breaks down some of the proteins a little bit, and some of the proteins may actually get taken back up by the Golgi and get recycled. And then if they get recycled, we can kind of do some modifications to them, repackage them and send them back out. So that's a cool concept. All right, my friends, this video now covers the Golgi apparatus, all the structure and the functional components. I hope it made sense. I hope that you guys liked it as always until next time. Transcribed by TurboScribe.ai. Go Unlimited to remove this message.