 There are two main types of cells. So all the cells on the planet can be divided into two main categories, and you will definitely be held accountable for being able to determine if I give you a cell, any cell, for telling me which of these two categories it fits into. Are you ready for your categories? Okay. There are prokaryotes, and there are eukaryotes. And let's just do a quick dissection of these words. What exactly do these words mean? Pro means before, and you means true. And this whole karyote thing, which is similar in both of them, it actually is referring, the word itself actually means kernel. I want you to think. Just go ahead, push pause if you have to, and think, what is a kernel? What could be considered a kernel inside a cell? What do you think? The nucleus, in fact, the kernel, okay, no, we're going to do it like this. The kernel is referring to the nucleus, which is in the center. And I'm going to tell you right now, just so you have some perspective, what's in the nucleus of a cell? Remember, I think it was the last characteristic in cell theory was that all cells have DNA. So inside the kernel, the nucleus is DNA. You could tell me, but we know all cells have DNA, but in a true kernel versus a before the kernel, I don't know if that's going to help anyone at all, or if it just makes it worse. Maybe I'll just tell you what it is. Eukaryotes have a nucleus, and prokaryotes do not have a nucleus. And we're going to talk about a nucleus. Like, what is this? In fact, look down here. There's a whole section just on the nucleus. And so we'll deal with, like, what exactly is this? What is its structure? What is its function? But we know that it has DNA inside of it. Both prokaryotes and eukaryotes have DNA. The eukaryotes just hold it in a little package, a little kernel called the nucleus. It's not the only thing. That is the thing that distinguishes between them, and there are some other characteristics that we can look at. For example, prokaryotes tend to be much smaller than eukaryotes. And I think of this as being like, okay, yeah, you know, they've got a big old nucleus that they have to fit in there. And eukaryotes have membrane-bound organelles. Organelles, remember, that was you use... Organelles are made out of biomolecules, and they're found inside a cell, but they're not yet alive. They are like the little machines that are doing their job inside the cells. And in eukaryotes, you have organelles that are literally surrounded by their own membranes. Whereas in prokaryotes, dude, there's not enough room to have cells with their own membrane-bound organelles inside of them. The prokaryote is the size of an organelle. So if you had a whole organelle inside the prokaryote, it is just a giant organelle, which some may argue that that's actually the case. These are generalized characteristics of these different categories. But like I said earlier, all cells, all of them, can be put into one of these two categories. So there are two different types of prokaryotes that we will learn, and that's kind of coming down the road. I think, I don't think we're going to talk about our two different types of prokaryotes. Maybe I should give you an example, though. An example of a prokaryote is bacteria. This is the most common. There is another kind of prokaryote. It's called an archaean, and they're kind of weird and cool. If you looked at one, you'd be like, dude, that's a bacteria, and they're extremely similar, but they're definitely distinct from each other. And we'll talk about that, like I said, later on down toward the end of the semester. Examples of eukaryotes, you are a eukaryote, a plant is a eukaryote, and that's the next topic. We're going to look at what are all the possible different eukaryotes that we can have.