Prokaryote Cell Structures
Prokaryotic Cell Structures 1
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hi in this video will be taking a look at pro carry its, which can be broken up into bacteria and archaea. Now, pro carry attic cells are significantly smaller than eukaryotic cells. And what differentiates them mainly from eukaryotic cells is that they lack a nucleus, and they lack membrane bound organelles. Now, as you can see in this diagram of a pro carry attic sell here, uh, the central region of the cell contains the nuclear oId, which is basically just condensed ball of most or all of the DNA that the organism contains now pro carry. It's also contain what are called plasmas, which are small molecules of DNA that are extra chromosome away, as in separate from the chromosome of cell. So you can see right here this is our nuclear Lloyd, and over here we have these little plasmids. Now you might recall that pro Kerasiotes have circular, double stranded DNA. Unlike you, Kerasiotes like us who have linear DNA now additionally pro carry. It's have a cell wall that's made of peptic like hand, and that's what gives the cells. They're shaped this rigid outer wall that you see here in red. That's what's going to give pro carry attic cells their shape. And again, um, this is in part because, unlike eukaryotic cells, which have a site of skeleton to maintain rigidity, uh, this cell wall is there, Thio, um, keep the cell from collapsing in on itself and and to maintain the proper structure Now, peptic Google I can is something we discussed way back when we talked about biological molecules. And you might recall that it is comprised of proteins that's the kept it apart and also carbohydrates. That's the Glick and component. And basically, what you have are these sugar chains, which I'm marking here in blue. These are sugar chains, right? That's our carbohydrate. And then we also have these little, uh, little peptides. You can see they're not very big there. Only a few amino acids long, right? So these are our peptides. And as the figure points out, technically these air illegal peptides and that determination comes from the number of amino acids in the chain. But that's really getting into the realm of biochemistry. You guys don't need to worry about that. All you really need to know about peptic, like in is that it's thes sugar chains that air Cross linked cross linked by a small peptides and that cross linking is what makes what makes thes cell walls so strong, right, this peptic like and this is a strong, resilient material. Now, not all bacterial cells have so or have, um, exterior structures that are similar. In fact, there's there's kind of, ah divide in bacteria, and it's based on the sustaining technique called the gram stain. So before we get into what the difference between Gram positive and gram negative bacteria is, I just want to point out that, um, this is a distinction defined by a test from a long time ago, right? So, uh, this microbiologist whose name was Graham that's where the name came from Name comes from came up with this staining technique, which uses, actually a variety of different stains. We're not going to get into the specifics of how it works, but eso don't You know, I point that out because don't think that the gram stain is actually just one stain. It's a type of technique that involves many stains and washing the cells and then applying new stains. It's actually a you know, kind of ah, longer procedure than this name implies. And essentially there's a pigment used right, a dye used that will be absorbed by peptide of like in. So essentially, this staining technique allows people to observe pep to dig like an in the cell walls of precarious oats. And, you know, this is they're looking through microscopes, of course, to see the cells. So basically some bacteria which have been dubbed gram positive bacteria because they have a positive test in there, they have a positive result in the gram stain. And that is because they have this thick kept it. A Gleicher hand layer, right could see this thick outer layer of peptic like. And so when the gram stain technique is done to these cells, lots of this particular stain called crystal Violet um is going to be absorbed into this thick layer of peptic like and so these cells are going to have a strong purple appearance due to that crystal violet stain. Now, gram negative bacteria actually have this outer membrane of Lippo. Polly Sacha rides. And let's pause there. What do you think? Lippo? Polly, Sacha rides are well, Lippo, right? That's gonna be lipid, right? and then Polly Sack rides. So it's, um, you know, again sugar chains with lipid attachments. So, um, again, just always be thinking about your prefixes and suffixes when you hear these biochemical names because they'll often reveal what it is we're talking about. So anyways, gram negative bacteria have this outer membrane of lipid Polly sack lipid Polly Sacha rides and then inside that they actually have this thin layer of peptic glikin. Right? So here's our peptic like an right. It's just this thin little layer. Our outer membrane may actually jump out of the image here. All right, outer membrane you can see marked here in green, that dark green color that is made up of lipid Polly Sack, Lippo, Polly, Sacha rides. And then, of course, we have the plasma membrane, this light green interior structure, right, and this blue light blue space that you see between the Pepto Google I can layer and the plasma membrane as well as the outer membrane that's actually called the Perry Plaza Mick space. And this is literally like a gap between these coatings of the cells of speak. Um, and it's actually super important for the realm of microbiology. We're not gonna get into it in our discussion. Just pointing out that there is a little little space there and you can see that in gram positive bacteria. They have just one of those little spaces because they don't have that outer membrane layer anyways. So, uh, this is a distinction often used to characterize bacteria. Are the gram negative? Are they gram positive? And really, it's just referring thio, uh, sort of how the cell organizes its outer structures, right. Do they have this thick, outer peptic like handler? Or do they have a little faith thinner, internal peptic like antler with this outer Lippo Polly Sacha ride membrane. And again, this is not a distinction. Um, you know, born out of how out of, you know, some bad, you know, evolutionary trend. This this is a distinction that is based upon a laboratory test called the Gram stain. So with that, let's flip the page
Prokaryotic Cell Structures 2
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some pro carry attic cells will actually have a new, additional outer coating called a capsule. Or sometimes it's referred to as the slime layer. I kind of love that name, to be honest. And this is a large Polly Sacha ride, uh, coding that will surround the cells. And it's It's basically a protective layer for the cell, right? Just another protective layer for that cell. Now some cells can form what are called endo spores, and these are, um, super resilient but dormant forms of bacteria. And they basically form in response thio either a lack of nutrients in the environment or some form of really harsh conditions. For example, some bacteria will, you know, form thes endo spores in response to you high heat or something like that. So the idea is when Thebes Bacteria realizes that it is compromised, right? It's going to die. There's not enough resource is the environment is getting super inhospitable. It will form this dormant endo spore so that it can, uh, you know, lay low, basically like hibernate almost for super long periods of time. And seriously, you know, we're talking like hundreds. Even thousands, uh, debated Lee even longer uh, periods of time before they will reactivate. And you can see just a bunch of examples of endo sports here. Three idea being that they come in all shapes and sizes. Uh, I don't really need to know anything specific about any of these and a sports. So just another defense mechanism that some bacteria have evolved in order. Thio avoid dying in harsh conditions. Now, last thing I want Thio talk about is how pro carry outs move around. And also what appendages thes cells you. So, um, some pro Kerasiotes have what are called Fibria, and and these kind of like to think of them as little arms because they're basically appendages that allow bacterial cells thio adhere to surfaces and you can see these little pink strands on this Sell those air Fibria and those are allowing the cell to adhere to the surface that it is attached to. Now, bacteria will also have what are called flow Gela for plural or flagellum singular. So you can see that this cell has a number of flu, Gela right, pointing them out with these red arrows. And these are kind of like kind of like whips in the way they move. You can see in this image here that basically they will kind of spin around. And essentially, they're used for locomotion and sensation so they can be used for the bacteria to actually move around. And, you know, if you think about it, it's kind of crazy. But, you know, these cells air so small that essentially the flu Gellar almost like boring through the medium, you know, like water, for example, essentially like boring through the water. So I like to think of them is like a Drehle or something. Almost, um, And again, you know, that just has to do with the comparative size of the bacteria to the force. The attractive forces of those molecules Now, interestingly, flagellum can also or flu Gela Rather could be also used for sensation. Um, so there are some that have evolved and been modified as a sensory appendages. Now the last type of penda I want to talk about is the Hillis. Sometimes it's called the Sex Pillows. And, um, this is a new appendage on the surface of many bacterial cells, and it's, uh, involved in this process called conjugation, that we're going to talk about Maurin depth when we discuss bacterial reproduction. But the basic idea is that this is sort of like a a tube through which bacteria can pass DNA. And again, we'll talk more about this concept later. But as you can see right here, this little bacterial cell in the diagram has this little appendage, the pillows and through this pillows that's going thio, move some of the DNA in this plasma. All right with that, let's actually turn the page.
Prokaryotic Cell Structures 3
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pro Kerasiotes bacteria and archaea make up 60% of Earth's biomass. And by that I mean, if you took all the living organisms of Earth and you put them on a scale right, 60% of the weight that you'd be reading on that scale would be due to pro carry Ah, tick cells, right. These little microscopic organisms, they were the first life forms, Uh, and they also happen to be the most prolific. They're everywhere. I mean, they're inside us there on our skin, there, inside other creatures. If you take a scoop of ocean water, you're going to get a ton of them in there. I mean, these guys air everywhere, and they're also crazy places to like deep sea hydrothermal events. Um, they're just amazing organisms. And the reason I'm saying all of this is because it is, in a sense, tragic. How little we really get to talk about them in introductory biology. Okay, so we're doing a quick review of them here, But by no means should you take that as an indication that these air unimportant or un interesting organisms there actually some of the most important, most interesting life forms on the planet. Um, introductory biology just tends to be a little more focused on Thebes, up of organisms that, you know, humans interact or visibly interact with on a day to day basis. Okay, so take microbiology. It's truly fascinating. And now we're going to briefly, you know, almost criminally briefly discuss archaea, which are pro carry. It's similar to bacteria, but they have certain features that differentiate them from bacteria. And, of course, you carry outs. So they're of a similar size and shape to bacteria. But unlike bacteria they do not use, kept it a glide hand in their cell walls. The chemical composition of their membranes is distinct from both bacteria and eukaryotes. Now, just like bacteria, they have a circular loop of DNA, right? That's their chromosome. You'll find it in a nuclear oId in the cell. Uh, they also lack membrane bound organelles and a nucleus. Right? So they are, you know, pro carry its. They have all those defining pro carry attic features. However, uh, there are some interesting differences between them and bacteria. For one, their genetic machinery that they used for transcription and translation right gene expression happens to be more similar to you carry outs than bacteria, which is pretty fascinating. And it's also one of the reasons that you carry outs are thought you have evolved from Arcadia, not bacteria. And you might notice that in our little tree of life down here, right, here's our our route. Right. That's sort of the origin point. And we have a pro are sorry. Bacteria. Oops. Bacteria here. And, um, thes in red. Are you Kerasiotes? And then actually in green here, we've got our Arcadia, and you can see that, uh, the eukaryotes and the archaea have a common ancestor. So, um, additionally, archaea reproduce a sexually similar to bacteria, but like bacteria, they're capable of form of forms of gene transfer. And we're going to get into how that works in a different video. So take away is archaea are similar to bacteria, but there are some biochemical differences that separate them as a class of organism. Now, the thing most people tend to know about Arcadia is that they're extremophiles. But this is actually, um and anecdotal. I mean, certainly there are many species of extremophiles within Arcadia, but there are many, many, many types of Arcadia that don't live in extreme environments, right? So, really, the whole RK are extremophiles is not a good generalization. Um, now, looking at, uh, taking a look at this image here, these air some really famous archaea which you will find in Yellowstone. This is what's known as the Grand prismatic pool. It is a a sulfur rich hot spring, and the archaea that live in there are known as thermal files, right? They like heat. And, uh, you know, they will live in these hot springs, which are, I don't know, close to boiling point roughly. Um, they can also be found in these deep sea hydrothermal events that exude incredibly, uh, hot, hot, hot temperatures. I mean, you know, uh, way beyond boiling point. Right? So, you know, they don't all just like the most extreme temperatures. They like a range of temperatures. And that's really the point I'm trying to impress in general. Is that archaic? Could be found in all different types of environments. Um, some cool ones that I happen to like are the hail of files. And these like to live in salty environments. Um, including environments as salty as the dead sea. Right. Just in has such a high salinity level that, you know, if you were to swim in it, you feel the difference in density of the water. You know, it just feels very thick. Uh, now, Bethany Jen's are a really cool type of Arcadia. They produce methane as a byproduct of their metabolism, and these air found all over the place, they live in swamps, right? That's that kind of funky gross smell that you smell in swamps is, um, from methane in part and that stupid myth antigens. And also they live in the guts of animals and cows, for example. Are ruminants have thes Muthanna genes that live inside them? And that's, um, where the methane that they fart comes from. Now, the last thing I want to point out is, you know, main theme of biology, structure, fits, function. Right. So, uh, here we have the normal sort of fost Philip ID. Um, phosphate lipid, bi layer. Right. This is composed of what you can kind of think of a generic or vanilla Foss. Philip, it's right. And this you'll find in, you know, just regular old pro Kerasiotes eukaryotes. Whatever. Here, On the other hand, we have are, um, fossil lipids from the hot spring bacteria, and you'll notice that the actual chemical structure of these is pretty different. Right? And it's made of these ice a cream units. That's what, uh, thes air called Don't worry about the name. The main point is these false Philippines will stick together much more tightly, which is how the membranes of these hot spring pro Kerasiotes will resist breaking down at those high temperatures. So again, like structure, fits function and you're going to see these biochemical differences between theme the cells of Arcadia and he sells off bacteria. All right, that's all I have for this video. I'll see you guys later.
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