by Jason Amores Sumpter
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in this video, we're going to talk about the first organ L of the Endo Membrane system, which is the nucleus, and so protein secretion is going to start in the nucleus. And this is because the nucleus of a eukaryotic cell stores the D N A of the cell and recall that the D N A of the cell carries the recipe or the code for making the protein. And so that's exactly why protein secretion starts in the nucleus, because you can't secrete the protein until after you've made the protein. Now the nucleus can be defined as a rounded structure that contains and protects most of a eukaryotic cells. D n A. Now there are these three structures that we're going to talk about, uh, in the nucleus that you all should be aware of. Now remember that the nucleus is part of the Endo membrane system, which means that its border is going to be a membrane itself, and the border of the nucleus has a specific name that we refer to as the nuclear envelope. And so the nuclear envelope is really just defining the double membrane barrier that surrounds the nucleus and again acts as the barrier of the nucleus, basically separating the inside of the nucleus from the outside of the nucleus. Now nuclear pores are referring to tiny little pores or holes that are found in the nuclear envelope. And these tiny little nuclear pores or holes in the nuclear envelope are going to allow the entry and exit into and out of the nucleus so they basically can control and monitor what leaves the nucleus and also what enters the nucleus. Now this other, uh, word here the nuclear Olis is referring to a small, dense structure that's on the inside of the nucleus. And this is specifically where rhizomes are assembled and recall from our previous lesson videos that ribosomes are important for making proteins, which is another reason why the nucleus is the first step of protein secretion because it is involved with making ribosomes. And so let's take a look at our image down below right here to get a better understanding of the eukaryotic nucleus. So over here on the left hand side, we're showing you our representation of the Eukaryotic cell and notice right here. We're showing you the nucleus of the cell, and so if we zoom in here to the nucleus of the cell, which will notice is that it is made up of a membrane, a double membrane, and this double membrane that you see here acts as the barrier of the nucleus. And so the gray structures that you see here are referring to the nuclear envelope. And so we can label this as the nuclear envelope, the double membrane that surrounds the nucleus and acts as its barrier. Basically, what you see surrounding the nucleus here. Now, notice that in the nuclear envelope there are these holes that you see throughout these pores, if you will, the nuclear pores. So this whole that you see right here in the nuclear envelope is referring to the nuclear pore. Now, notice that on the inside of the nucleus we have d n A. And so these structures that you see here represent DNA and the DNA. Most of the Eukaryotic cell's DNA is found inside of the nucleus, so that's important to keep in mind now, also within the nucleus right here at the core of the nucleus. There's another small, dense structure on the inside of the nucleus, and this is where ribosomes are going to be assembled. So this is specifically the new CLee Olis. So this is the nuclear Alissa structure within the inside of the nucleus itself that is involved with building or assembling rhizomes. Now, the reason, once again that, uh, the protein secretion process starts in the nucleus is because the nucleus is what is going to contain the d n a of the cell. And so the DNA of a cell which is again found in the nucleus of the cell, is going to be transcribed into RNA, and then the RNA will then be translated into a protein itself. And, uh, the protein recall is being built by the Riva Zone. And there's gonna be a lot more details on this process that we're mentioning right here. Later, in our course on, we'll talk more about this idea of transcription or being transcribed as well as translation again later in our course. For now, what you should note is that protein secretion starts in the nucleus because in order for a protein to be made, it first needs the DNA in the nucleus needs to be transcribed into RNA, and then the Arna needs to be translated into the protein, and then once the protein is made, it can then be secreted. And so this year concludes our introduction to the nucleus, and we'll be able to talk more about the other organelles at the end of membrane system moving forward in our course. So I'll see you guys in our next video.