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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

13. Intracellular Protein Transport




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Hi in this video we're gonna be talking about x acidosis. So x acidosis is the process of secreting molecules outside the cell is the process of getting things out. So there are two main pathways. The first is the constitutive Secretary pathway. And this is gonna be a pathway that operates all the time just continuously. And it's going to be the default pathway. So most things that need to get out of the cell are just gonna go through this pathway and it's just constantly running constantly getting rid of things. Um This is the pathway also that that supplies the plasma membrane with newly synthesized lipids. So the plasma membrane just doesn't exist for all eternity. It constantly needs to be replaced. And so this pathway brings those new lipids to the plasma membrane in the process of secreting something else. Now there's also a separate pathway. This is the regulated Secretary pathway. And so this occurs only in specialized cells that produce and release a lot of molecule. And so how this pathway works is it's got this continuous pathway instead. Special secret ori vesicles actually store whatever molecule needs to be released. Um And they bud from the golgi and they dock. So they just kind of sit at the plasma membrane waiting for their release when they get some type of signal signal. Usually the signals calcium, but it can be other things. The vessels will fuse and release all that material into the exercise environment. This is really common in nerve cells. And so both of these vesicles that are, you know, taking up material somewhere in the gold here, somewhere in the cell and transporting them out, travel on micro tubules which guide vesicles to the cell service. So, here's an example of the regulatory Secretary pathway. So you see these vesicles, these are actually narrow transmitters. They have lots of the same molecule in them. And so they sit really close to the plasma membrane. And when a chemical signal comes in, so for, say, calcium, this results in fusion and release of these molecules in extra cellular early, which can then go on and do other things like in nerve for a neuron transmission, neurotransmitter transmission. But exhaust psychosis really occurs in four steps. So the first thing is that there's a vesicles, It's carrying something that's carrying a cargo and it moves towards the plasma membrane. Um now it doesn't necessarily move everywhere in the plasma membrane. Right? There are specific domains of the plasma membrane that exists. So, for instance, polarized membranes have different domains, which means one section of the plasma membrane is different chemically than another section. And so, vesicles are usually targeted to one domain only and not all of them. And this is through various sorting signals. Very common in cell biology. Once the bicycle is headed towards the right area of the plasma membrane, it's going to eventually fuse those contents are released into the extra cellular environment and the membrane infusion causes the membrane to become larger because there's more membrane there, luckily the cell well, isn't just entirely growing just larger and larger and larger every time something needs to be excessive toast because the opposite indo psychosis molecules entering the cell will actually take that extra membrane and bring it into the cell. So here we have a vested confusion, we have a vesicles. It's headed towards the plasma membrane. It can dock really close here, it releases it, fuses, releases its content, and eventually this entire membrane will be added to the membrane infused with in this case the plasma membrane. But that's okay because endo psychosis will take that extra membrane and bring it back into the south. So that is the process of exhaust psychosis. So now let's turn the page.

Which of the following is not a pathway of exocytosis?


When a vesicle fuses to the plasma membrane what happens to the lipids in the vesicles?