Prokaryotic and eukaryotic cells
- [Voiceover] When we wanna categorize life as we know it at a very high level, we can categorize it as either eukaryotic, eukaryotic or as a eukaryote, eukaryote, or as a prokaryote, prokaryote. And the largest distinction between a eukaryote and a prokaryote are membrane-bound structures that eukaryotes have that prokaryotes don't have. The most noticeable of which is a membrane-bound nucleus. So in a eukaryote, the genetic information is going to be inside a membrane-bound nucleus. So this right over here, this is the nucleus. This is the nucleus and you have your genetic information inside it, you have your DNA. Here, for a prokaryotic cell, you're going to have your DNA. It might be bundled up into a section of the cell. We would call that a nucleoid but it's not membrane-bound. So let me we write this down no membrane... Let me write a little membrane-bound, membrane-bound nucleus. But that's not the only distinction in between eukaryotes and prokaryotes. It's almost the one that's most noted. In fact, the word eukaryote, the karyote part comes from the Greek for nut or kernel. So let me make this clear. So this is referring to a nut or a kernel while prokaryote means before the nut or kernel. So we don't see and you know, I just could think of the nut or the kernel as the membrane-bound structure, especially the membrane-bound nucleus over here. But that's not all. Eukaryotes will also have other membrane-bound structures that you will not see in prokaryotes. For example, you will tend to see mitochondria, mitochondria, in a eukaryotic cell, both plant and animal cells, but you won't see it in a prokaryotic cell. And there's other types of membrane-bound structures. You could see things like Golgi apparatus. This over here is a micrograph of a eukaryotic cell. And you see the Golgi apparatus, right over here, which helps package proteins. You see a micrograph of mitrochondria. This is a micrograph of the nucleus. So this, right over here, is the nuclear membrane. And then you see all the genetic information. It's all spread out. It's in chromatin form right over here but you see it's especially densely packed right over here. And we've also put it in this and right over there. So this is all the DNA in chromatin form but this part that looks extra dense or dark in this micrograph right over there, we call that the nucleolus. We call that the nucleolus. And we now know that this is where ribosomal RNA is being produced. And ribosomal RNA, that forms part of the structure of ribosomes which are essential in the translation, well I guess you can say, the construction of proteins based on the information in mRNA. We'll go into a lot more depth in that in other videos. So these are ribosomes right over here and they're made up of ribosomal RNA and they're also made up of proteins. And so this nucleolus over there, that's where that's happening, that denser part of the nucleus. So the key distinction, eukaryotic cell, you have a membrane-bounded nucleus, you have other membrane-bound structures like mitochondria. In fact, there's some theories that mitochondria first evolved as prokaryotic organisms that eventually lived in symbiosis inside of a larger eukaryotic cell. And then the other distinction is that in eukaryotes, the DNA tends to be in multiple strands. So the DNA, if you were to kinda straighten it out, it would be in multiple strands. On a prokaryote, the DNA tends to be circular. It can be all flipped around and whatever else but at the end of the day, it would be circular DNA. So those are the three core distinctions: nuclear membrane, other membrane-bound organelles, like mitochondria and the Golgi apparatus, and then you also have multiple single strands of DNA versus circular DNA. Other things is that eukaryotes tend to be larger, while prokaryotes tend to be smaller, they tend to be simpler. So now that we know the key distinctions, what are examples of eukaryotes? Well, eukaryotes include most of what we interact with on a daily basis or we think we're interacting with on a daily basis. These includes all multicellular organisms, so multicellular, multicellular organisms. So I'm thinking animals, plants, fungi. It includes protists. This is a paramuseum right over here. This is eukaryotic. It's going to have a membrane-bound nucleus and other organelles. This right over here, these are onion root tip cells. So these are plant cells. And you could actually see it's been stained You can actually see the membrane-bound nucleus here. And this is actually a cool picture because you can see the cells at different stages of mitosis, which is interesting. Animal cells, the things that make you you, you are eukaryotic. So what is prokaryotic? Well, bacteria is probably the most common example of that. Bacteria, right over here, these are prokaryotes. And the lesser talk or things that's talked about lot less is archaea. And archaea, people initially thought that these were a form of bacteria that just lived in vary extreme conditions. But now they know it's a completely different domain of life, archaea. And so when we think about the domains of life, the current thought is that you have bacteria here, bacteria here, you have archaea. You have archaea, And then you have, and then you have eukaryotes. I'll do it there, and then you have eukaryotes. And these are things that have all of the traits that we've talked about and so this include plants and animals and fungi and unicellular eukaryotes, protists, and things like that. And so, if we once again, just high level we would consider these prokaryotes and these of course are the eukaryotes. So hopefully that gives you a good overview of things.
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