Untitled Flashcard Set

in this video, we're going to begin a look at the largest of the organelles found within the cell. This is the nucleus here. What I've done is I've taken a little blood smear, which we've looked at under a microscope and taken a photograph of. And you can see a blood smear is made up of these very round pale cells. These are the red blood cells. Red blood cells actually don't contain a nucleus. So therefore we call them anucleate it. Whenever you put a in front of 'a' word, it means without, anucleate someone who is amoral has without morals. Here. We've got this cell, though, with this big purple blob inside of it. This is the nucleus of this white blood cell. So we say this cell is nucleated. Here. We can see. Remember our stylisted cell diagram here. And we have this large structure here, which is the nucleus, the largest of the organelles within our cells. And you can see how large it is here. We have a look at a higher magnified view of that is the nucleus. Um, it's got all these different components. So what are these different components? Well, just like the cell has an encasing membrane. The nucleus also has an encasing membrane. It's known as the nuclear membrane or the nuclear envelope. Um, so it's just the name for the membrane around the outside of the nucleus, Um, and obviously, just like a cell membrane, it's going to regulate what can enter and exit the nucleus, um, and the things which helped enable things to move from to and from the nucleus are these little paws, and these are called nuclear pore. So they're in the nuclear envelope itself that allow communication between the inside of the nucleus and the cytoplasm where the rest of the organelles and cytosol is inside the nucleus. We find Chromatin; Chromatin is the store of DNA inside the nucleus, and there's different types of Chromatin, which we'll talk about in a little while. But basically that's where our store of DNA is, and DNA is an act together with proteins. And so together. The DNA and the proteins, which are packed together are referred to as chromatin; And inside the nucleus we have this little area dark clump area, which is known as the nucleolus, so it's like nucleus. But it's a little nucleus inside the nucleus, and we call it a nucleolus. It's not really a little nucleus inside the nucleus, but that's the why where its name comes from. So this is a magnified view of one of these nuclear pores you can actually see. It's a little channel that allows communication between the. cytosol on the outside and the nucleoplasm, which we'll see in a second on the inside the nuclear envelope or the nuclear membrane is the outer boundary of the nucleus and, incases, the nucleoplasm. So while the cell membrane incases the cytoplasm, the nucleus has a nuclear envelope or nuclear membrane, which incases the nucleoplasm, it separates the nucleus from the cytoplasm and the cytosol. It consists of a double membrane, so 2 phospholipid layers, one here and one here, which means there's a little space in between. The two; Communicates with the cytoplasm via channels called nuclear pores as we can see, nuclear pores comprise about 10% of the nuclear envelope, allows cellular communication or sorry chemical communication between the cytosol, which is the fluid part of the cytoplasm, if you remember, and the nucleoplasm, which is the fluid part of the nucleus, it helps to regulate movement of ions, ribosomes, messenger RNA and other small molecules. Now, some of these words may not make any sense to you just yet, but we will come up to ribosomes and what messenger RNA is, and so on. So in this is the nucleoplasm we have. What what I referred to before. Um, fluid gel like substance containing DNA, uh, contains distinct Chromatin region. So Chromatin, if you remember, is the DNA plus the proteins inside the nucleus. And they have distinct Chromatin regions called you Euchromatin, which are lighter areas, which means that the DNA. Is can either be compacted and stored in the nucleus or if it's active and making messenger RNA, which is the primary function. Um, then it's unzipped and therefore stains less intensely because it's not packed up. And so we call that Euchromatin. So the more pale euchromatin there is in a nucleus, the more transcriptionally active. That cell is; heterochromatin. is the opposite of you, euchromatin. So when DNA is not being making messenger RNA, it gets packed up inside the nucleus. You can see some dark areas here on the outside. This is heterochromatin, so these light areas are the euchromatin and the dark areas of the heterochromatin. These are transcriptionally inactive areas, areas of the chromatin that aren't involved in making messenger RNA; contains the ions, enzymes, RNA and DNA. Nucleotides as well contains the nuclear matrix, which is sort of like a cytoskeleton for the nucleus holding everything in place, the network of fine filaments that provides structural support for the contents of the nucleus. So within the nucleus, we have the nucleolus. Or, if there's more than one, we call them nucleoli Um, so nucleoli the plural, nucleolus is the singular form, so the cell may have one or more nucleoli. Um, if it's only got one, we say it's the nucleolus, so this is a transient nuclear organelles. That's responsible for the production of ribosomes. Now Ribosomes are a non membranous organelles. They're involved in the production of proteins they are. the site where proteins get made, and so they're made up of their own type of material. Nucleic acids called ribosomes, or nucleic acids. And in this specific case, Ryba zonal ribonucleic acids. So rRNA is how you pronounce this, rRNA. We have different types of RNA. We just talked about mRNA, Messenger RNA. There's a third type called Transfer RNA or tRNA. We'll talk more about that when we look at the way cells make proteins. But at the moment, all you need to know is that the nucleolus is the site for production of ribosomes. Um, and so, of course, they need to be able to get from the inside of the nucleus to the outside in the cytoplasm. And so they do that through those nuclear pores that we talked before. The nucleolus is composed of RNA is composed of enzymes as well as proteins known as his histones and chromatin, which we just mentioned before, as well as also made up of histones; nucleoli or a nucleolus is most prominent cells that produce large amounts of proteins, which kind of makes sense. If ribosomes are making proteins, then you want to be making lots of ribosomes. The other thing. Of course, if you're making proteins, you need the messenger RNA, which will find more out about a little bit later. But just to preempt it. Messenger RNA makes the proteins that ribosomes, and so if you've got lots of messenger RNA, therefore, you've got lots of Euchromatin . A lots of pale staining chromatin means that you can see the nucleolus is much more easily as well, much more readily. So liver cells, which produce large amounts protein, lots of, um, if you ever get a blood test, you might get a liver function looking at the your blood enzymes. Those are your liver enzymes because they're actually producing things like albumin and things like that. So those liver cells produce a lot of the plasma proteins in your blood that they produce lots of, um, lots of proteins, and therefore they have a prominent nucleolus or even more than one nucleolus. Nerve cells and muscle cells also have prominent nucleolis. as well. Okay, that ends this video. In the next video, we'll be looking at more detail about the processes that take place within the nucleus