13. Intracellular Protein Transport
Endocytic Pathways
1
concept
Types of Endocytosis
2m
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Hi in this video we're gonna be talking about and acidic pathways. So there are three types of in acidic pathways um and each one of them have in common. The fact that they bring some type of fluid or molecule into the cell. So the first is gonna be pinot psychosis. You've heard about this in your bio 101 class that's gonna be sell drinking so it brings fluid into the cell. Then you have to go psychosis that's gonna be the cell eating. And so that's gonna bring large molecules into the cell. And so uh Magas OEMs which are the things that take in these large molecules end up fusing with license OEMs to degrade most of these molecules. So that's kind of like you know you eat your esophagus takes your food to your stomach to degrade well um you know you faggots, I toast something, it a zone carries it to the license. Um and licensing degrades it. It's the same thing then you have receptor mediated induced psychosis. Now this is a really specific so the rest of these like fluid it just kind of whatever fluids around large molecules whatever large molecules around. But receptor mediated induced psychosis is really specific and that brings only specific molecules into the cell. So how it happens is it uses clattering coated pits for the most part and um these bind receptors that select cargo specific cargo for entry. So we hear a lot about cholesterols and LDL and HDL S and things and I'm not gonna go into how that entire process but receptor mediated into psychosis is the way that your cells take in these L. D. L. S. Um and that regulates your cholesterol. Now sometimes um receptor mediated induce ketosis can use caveat hole. And these are just small imaginations of the membrane. And that also brings specific molecules into the cell. So they're kind of the two ways that our M. E. Or receptor mediated into psychosis works. So let me back out here and you can see the three different ways you have psychosis bringing up some type of large molecule into the cell into a bag. A zone you have pen acidosis which brings fluid mainly fluid into mescal into the cell. And then you have receptor mediated into psychosis which brings really specific molecules. So only the star into the cell. So with that let's not move on.
2
concept
Endosomal Sorting
12m
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Hello, everyone in this lesson, we're going to be talking about into zones and their functions. Okay, so we've previously learned about bulk transport and the way that some substances enter into the cell via imagination of the cellular membrane and then the formation of a vesicles holding that stuff or whatever was imported into the cell. And that was in our last lesson. Now, we're going to talk about specific specialized vesicles and their jobs once the cargo has entered into the cell. So we're gonna be talking about into zones and their abilities in indo zonal sorting into zones are going to be large organ al sorting hubs and these are going to be specialized vesicles that hold a variety of different materials that enter and exit the cell. And basically the job of the indo zones is to sort the important things and throw away the not important things and to take the cargo to its next destination or send it on its way. And we're going to talk about two types of into zones. We're going to talk about early and late into zones. So, early into zones are obviously going to happen first. And these are going to be the indo zones, or specialized vesicles that are most closely associated with the plasma membrane. So, whenever the plasma membrane does bulk endo psychosis or the bringing in of material into the cell via a vesicles that vesicles is going to then fuse with an early into zone and then the early in the zone is going to begin sorting the contents of that vesicles. They are slightly acidic in comparison to the site is all but not terribly acidic? And they are going to sort the incoming material? And then they're going to send it to its next location. Now, late into zones are a little bit different. So early into zones, whenever they find something that needs to be destroyed or degraded or recycled, they're going to send it to the license zone, which is going to be the organelles that breaks cellular material down. So the early in twosomes, once they've tagged something for the destination of the license zone, then they're going to give it to the late into zones. The late zones are much more acidic and they are going to begin breaking things down and sorting things that are going to be transported to the license zone. I don't know that. You need to know all of that. You guys will probably learn more about this in more depth in other biology lessons, but I just wanted to give you an overview of the different types of Hinduism's, but I'm not really sure you're going to need to know all of those different types and their functions. Now, we're also going to talk about multi vesicular bodies, which if you wanted to shorten this name, it's M. V bees and they are going to be when in vaginal nations form inside of an indoor zone. And you might be thinking, what would be the point of that? Right? And imagination is utilized to form a vest which then fuses with an indo zone. Why would an India's own want to make an imagination of itself? Well, what if that India's own is carrying these cell membrane proteins or receptors that need to be degraded? Well, they're going to have to take those proteins inside of the indus zone. So there's going to have to be an inv imagination of that section of the plasma membrane of the indo zone to bring those receptors and those proteins from that membrane into the inside of the end zone. I hope that makes sense. We're going to look at this diagram right now and see if we can go over these different types of India zones and M V. B s. Okay, Alright, so, let's have a look at our diagram here. And this is going to be a diagram of a cell and the different windows, OEMs vesicles and M V. B. S that we just talked about. So, first off, let's start with the membrane bound protein. Perhaps this cell wants to transport or remove or do something with the membrane bound protein. So it's going to have to take it out of the membrane. You can see an inv agin ation of the plasma membrane actually happening right here. So that membrane is dipping down into the side is all and then we're going to form a vehicle. So, this guy here is going to be a vesicles And then that vesicles going to go on and fuse with the into zone. Now, I want you to notice something that membrane bound protein has been tagged with this little blue particle called ubiquity in whenever a protein is tagged with ubiquity in that means that that protein is destined for destruction. Where is it going to go? It's going to go to the light zone. Right, so that means that it needs to go into a late into zone. So whenever the imagination happens, that membrane bound proteins is taken into a vesicles, then that vesicles going to fuse with an indoor zone and then that into zone is going to become a late into zone and take that membrane bound protein too the license zone. But remember that with membrane bound proteins, the indo zone is going to have to do something important. It's going to have to make a multi vascular body or an M. V. B. Because we need that membrane bound protein inside of the indo zone, not on the outer edge of the end zone. So you can actually see another imagination happening in the end zone itself. Right here. You can see that membrane bound proteins actually kind of dipping down into the end zone. And then you can see they're actually what looked like tiny vesicles inside of the end zone. Those are going to be our M. V. B. S. So now the membrane bound protein is inside of the late in the zone and the late into zone is going to fuse with the license. Um over here and you're going to see that these M. V. B. S are going to enter into the license um so that those proteins on the M. B. B. S can be degraded. So that's going to be an overview of how indo psychosis and India's OEMs, M VBS and license OEMs work together to destroy certain molecules or to move certain molecules around. Now let's go down and instead of talking about into zones utilized for the destruction of cellular components, we're going to talk about some of the other things that they do like recycling and transportation. So into zones are going to be slightly acidic. Like I said, early into zones are less acidic than late into zones and late into zones are less acidic than life zones. And they are going to be act as compartments that are going to make the receptors that they hold release their cargo. So the change in ph is going to change the confirmation of the proteins that they hold inside of them. And those receptors proteins are then going to release whatever cargo or whatever molecule they are bound to. This is important. Especially if that molecule that is bound to the receptor needs to go somewhere else inside of the cell. So basically think about it as there's a receptor on the plasma membrane it binds to something. But now, what does it do with it? Well, it imagine. Eights into a vest ical. Then it goes into an into zone and because the into zone is going to be acidic, that cargo is going to be released and then that cargo can be transported somewhere else. And the receptor is put back into the plasma membrane and that's going to be what's happening in recycling in twosomes, recycling into zones are going to carry those receptors back to the plasma membrane. And this is so the receptors aren't destroyed because they're still functional and they can just go right back into the plasma membrane and try to capture another cargo. And then the cargo can travel to the license. Um If it is a toxic agent or some sort of agent that needs to be destroyed or it can go to another organ l wherever it is needed. Maybe it's some type of nutrients, some needed molecule that needs to be transported to a different organ l recycling into zones are really good at that. Now we're also going to talk about Transito sis transito sis I believe basically the transportation of molecules via and into zone. So Transito sis is going to be the process that occurs when the cargo remains attached to the receptor. So even though into zones are slightly acidic, these particular receptors don't don't change their confirmation and they don't let go of their cargo and this is going to allow the receptor and the cargo to travel to a different cellular location. Generally it's from one side of the cell to the other side of the cell and that cargo remains bound to the receptors and ends up wherever the receptor ends up. This is important, especially if you're transporting things to different areas of the cell and you want to keep the cargo with the cellular receptor and a lot of the time cells are going to want to do that. So down here, we're going to see this image of the transito sis happening and the recycling into zones doing their job. So you can see an inv agin ation in the plasma membrane occurring right here. And you can see that this particular receptor has bound to its little black circle which is going to be its cargo. So then we can see that that vesicles is going to fuse with the indo zone and you can see that the cargo is inside of the end zone. And because the end zone is acidic, we're going to see that this cargo is going to be released and then it's going to end up floating inside of the indo zone. And that then would have another option. And then we'd have um a India's own carrying the cargo. And then it goes wherever it needs to go. Maybe it's going to go to the Golgi body and it can be used there. Maybe it's going to go to the mitochondria and it can be used there. And then you can see that the receptor is actually going back to the plasma membrane and this is the recycling into zone. As you can see right here, this is the recycling into zone that is returning that receptor back to the plasma membrane so it can do its job. And then this one right here is going to go off to another organ. L. So another organ L. That needs this particular cargo piece. So that's going to be how the recycling into zone works and how those receptors get back into the plasma membrane. Now, what if we took this other tract? What if we took this tract right here? This is going to be the Transito SIS pathway. So if the receptor did not release its cargo. So let's say it did not do this. If it did not release its cargo, then what's going to happen? Well then it's going to travel down in its into zone or its little specialized vesicles and it's going to travel down and then it's going to attach to the other side of the plasma membrane where the into zone will fuse with the plasma membrane and it will actually attach the cargo and the receptor to the other side of the plasma plasma membrane. This is basically transporting the cargo and its receptor from one side to the other or from the plasma membrane to another organ. L. That's also possible as well. So that is going to be the process of Transito SIs, which is the other option for these particular individuals depending on the type of receptor and cargo that they are working with. This is very very important, especially when you have cells that have specific jobs happening on different sides of the sea. So for example if you guys look up what a stomach cell, endothelial iem cell looks like, you'll see that one side of the cell has one job and one side of the cell has the other job. So they are constantly transporting different receptors and different proteins via Transito Sis. So they will move things like that. Also the intestinal epithelial cells do this as well. Okay, so I know we went over a lot there. I hope it wasn't too terribly confusing. Just remember that into zones are very important. They can be utilized for recycling different receptors. They can be utilized for Transito sis and they can also be utilized for sorting and recycling of different cellular components by fusing with the license. Um Okay, everyone, let's go on to our next topic.
3
concept
Cholesterol LDL Uptake
2m
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okay in this video we're gonna be talking about cholesterol or LDL uptake. So this is going to be an example that you hear about a lot especially of receptor mediated into psychosis. And so I'm going to just try to walk you through and explain how this happened so that you understand all the different sorting mechanisms and ways that this occurs. So receptor mediated into psychosis is responsible for taking up cholesterol from the bloodstream. Now L. D. L. S are low density lipoproteins are the main form of cholesterol found in the blood. And so LDL receptors are found on a bunch of different plasma membranes but especially in cells that need to take up that cholesterol. And so when the cell decides oh I need more cholesterol, what it does is it makes these LDL receptors and places them in the plasma membrane. Right? That makes sense, needs more. Well it has to have a receptor for it. So it makes those receptors and eventually um those receptors um diffuse throughout the membrane. So they have around the entire cell and eventually they come in contact with classroom coded pits. Now they're already kind of pre assembled or really close to this classroom coded pit. And so when the LDL bind the receptors bind the LDL this allows for adaptor protein to interact very quickly the classroom coded pit then quickly forms and LDL is internalized And so you can imagine that people with mutations in this receptor have either a really great time like are very easily able to accept a lot of cholesterol or a hard time taking in a lot of cholesterol. So for instance, high blood cholesterol can run in families because they have a mutation in this LDL receptor that allows um that prevents the uptake of cholesterol into the cell and so it gets left in the blood. So you end up with this high blood cholesterol. So here we have a diagram of LDL. So here's LDL, this triangle thing and you have your LDL receptor then um whenever it binds this triggers classroom coded pit formation and the classroom will eventually leave where the LDL receptor actually go into the cell um and do cholesterol things. So you can imagine if that there's a mutation here the LDL is not going to bind and that's going to result in LDL being kept in the bloodstream and resulting in high blood cholesterol. So that's a great example of receptor mediated ketosis and cholesterol. So with that let's not move on.
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Problem
ProblemWhich of the following is not an endocytic pathway?
A
Receptor-mediate endocytosis
B
Pinocytosis
C
Fluid uptake
D
Phagocytosis
5
Problem
ProblemWhich vesicle is responsible for carrying receptors back to the plasma membrane?
A
Early endosomes
B
Late endosomes
C
Recycling endosomes
D
Multivesicular bodies
6
Problem
ProblemHigh blood cholesterol develops when what happens to the LDL receptor?
A
Too much LDL receptor is produced
B
Too little LDL receptor is produced
C
LDL binds the LDL receptor
D
The cell takes in too much LDL in clathrin coated pits