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Main content
Current time:0:00Total duration:11:40
AP.BIO:
SYI‑1 (EU)
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SYI‑1.E.1 (EK)

Video transcript

we've already talked about the process from going from DNA to messenger RNA and we call that process transcription and this occurs in the nucleus in the nucleus and then that messenger RNA makes it makes its way outside of the nucleus and it attaches to a ribosome and then it is translated into a protein it is translated into a protein and so you could say that this is this part right over here this is happening as this is being facilitated by a ribosome or it's happening at a ribosome with that high-level overview I now want to think a little bit in more detail about the how this actually happens or the structure of things where this happens inside of a cell and so I'm going to now draw the nucleus and a little bit more detail so that we can really see what's happening on its membrane so this right over here this over here is the nucleus actually let me draw it like this and instead of just drawing it just drawing the nucleus with one single line I'm going to draw it with two lines because it's actually a double by lipid membrane so this is 1 by lipid layer right over here and then this is another one right over here and I'm not viously not drawing it to scale I'm drawing it so that you can get a sense of things so each of these lines that I'm drawing if I were to zoom in on this so if I were to zoom in on each of these lines so let's zoom in and if I got a box like that you would see you would see a by lipid layer so a by lipid layer looks like this you have the circle as a hydrophilic end and those lines are the fatty hydrophobic ends so that's our by lipid layer so that's each of these each of these lines that I have drawn each of them are a bi lipid layer so the question is well how does the mRNA obviously you have all this transcription going on you have the DNA you have the mRNA it's all in here this big jumble of chromatin inside the nucleus how does it make its way out side of this by lipid outside of this double by lipid layer and the way it makes it way out is through nuclear pores so a nuclear pore a nuclear pore is essentially a tunnel and there are thousands of these is a tunnel through this by lipid layer so and the tunnel is made up of a bunch of proteins so this right over here and this is kind of a cross section of it but you could almost imagine it if you're thinking of it in three dimensions you would imagine a a tunnel a protein constructed a tunnel made out of proteins that goes through that goes through this this double by lipid membrane and so the mRNA so the mRNA can make its way out the mRNA can make its way out and get to a free ribosome and get to a free ribosome and then be translated into a protein and then be translated into a protein but this right over here is not the complete picture because when you when you translate a protein using a free ribosome this is for proteins that are used inside the cell so let me draw the entire cell right over here so this is entire this is the cell this right over here is the cytosol of the cell cytosol and you might be sometimes confused with the term cytosol and cytoplasm cytosol is all the fluid between the organelles cytoplasm is everything that's inside the cell so it's the cytosol and the organelles and the stuff inside the organelles is the cytoplasm so cytoplasm is everything inside of the cell cytosol is just the fluid that's between the organelles so anyway the free ribosome over here this term this translation is good for proteins used within the cell itself the proteins will can then fold around the cytosol and used in whichever way is appropriate but how do you get protein outside of the cell or even inside the cellular membrane ah'd within it within the cell but embedded in the cell membrane or outside of the cell itself and we know that cells communicate in all sorts of different way season they produce proteins for other cells or for use in the bloodstream or whatever it might be and that's what we're going to focus on in this video so contiguous with this with this what's called the para nuclear space right over here so the space between these two membranes so you have this para nuclear space between the inner and outer nuclear membrane let me just label that that's the inner nuclear membrane that's the outer nuclear membrane you could continue you could continue this outer nuclear membrane and you would and you get into these kind of flaps and folds and Bunge bulges and this right over here is considered a separate organelle so you get this thing that looks like this and I'll just do it how the best that I can draw it and this right over here is called the endoplasmic reticulum so this right here is endo endoplasmic reticulum which I've always thought would be a good name for band and the endoplasmic reticulum is key for starting to produce and then later on packaged proteins that are used for that are either embedded in the cellular membrane or used outside of the cell itself so how does that happen well the endoplasmic reticulum really has two regions it has the rough endoplasmic reticulum and the rough endoplasmic and hope plasmic reticulum has a bunch of ribosomes so that's a free ribosome right over here this is an attached ribosome this is a ribosome these are ribosomes that are attached to the membrane of the endoplasmic reticulum so this region where you have attached ribosomes right over here that is the rough that is the rough endoplasmic reticulum I'll call it the rough ER for short perhaps an even better name for a band and then there's another region which is a smooth endoplasmic reticulum and the role that this plays in protein synthesis or at least getting proteins ready for the outside of the cell is you can have messenger RNA messenger RNA right that lighter green color you can have messenger RNA find one of these ribosomes associated with the rough endoplasmic reticulum and as the protein is translated it won't be translated inside the cytosol it'll be translated on the other side of the rough endoplasmic endoplasmic reticulum or you could say on the inside of it on the lumen or in the lumen of the rough endoplasmic the rough endoplasmic reticulum let me make that a little bit let me draw that a little bit better so let's say that this right over here that right over here is the membrane of the endoplasmic reticulum and then as a as a protein or as an mRNA is being translated into protein the ribosome can attach and add the let's say that this right over here this right over here is the mRNA that is being translated let's say it's being it's going in that direction right over here here is the membrane of the ER so ER membrane ER membrane this right over here and actually the way I've drawn it right over here this is just one by lipid layer so let me just I could draw like this I could do it like this and this is actually this by lipid layer is continuous it's continuous with the outer nuclear membrane so let me just make it make it like that so you get the picture and then at some point of the in the trench in the translation process the protein can be spit out on the inside on the inside as as it's being translated it can be spit out on the inside of the endoplasmic reticulum so this is the lumen this is the ER lumen right over here so we're inside the the endoplasmic reticulum here here or outside here we're outside outside in the cytosol in the soundest in the in the side is the outside in the cytosol so that way you get the protein now inside the ER inside the endoplasmic reticulum it can travel through it and at some point it can but off so let's say imagine the protein is right over here and the smooth endoplasmic reticulum has many functions and I won't go into all of the depth of what how it's involved but at some point that protein can butt off and so let me draw a budding off protein so let's say this is a this is the the membrane of the endoplasmic reticulum and a protein let's say ends up ends up right over here and then it can butt out so I could go from that to what let me do that same color go from that to that do that I think you see where this is going do that and then to that then it could go to something like this to something like this now it has butted out and when you have a protein or really you have anything that's being transported around a cell with its own little mini membrane we call this a vesicle so now it'll bundle up and now is a vesicle now this vesicle can then let me draw let me draw some of these vesicles holding some proteins so let me draw that can then go to the Golgi apparatus the Golgi apparatus which I'll draw in blue right over here as best as I can so the Golgi apparatus this is not obviously there could be better drawings of something like this and then they can essentially do the reverse process and they can attach themselves to the Golgi oftentimes the Golgi body named after mr. Golgi who discovered this and then the proteins once they get into the inside of the Golgi body then they essentially go into a maturation process so that they're ready for transport outside of the cell or it may be to be embedded into the cellular membrane so this right over here is the Golgi body or a Golgi body or Golgi apparatus Golgi apparatus apparatus or Golgi body and then once they're done with that with that process then this is kind of them the fully manufactured protein ready to be used ready to be used and actually how maybe maybe I'll make it a slightly different well just use that same color this is the fully manufactured protein and now it can transport to the cell membrane and it can that protein can either be transported outside of the cell or it can be embedded within the membrane itself
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