Peptidoglycan

in this video, we're going to introduce the poly Sacha ride Pep Tito Glide can. So the poly Sacha ride Pep Tito Glide can is a hetero Polly Sacha ride which, of course, we know from our previous lesson videos just means that Petito glide can structure consists of at least two different types of repeating sugar units. And so these repeating sugar units are going to be the nag sugar molecule, which is the same sugar molecule that we covered in our previous lesson video of chitin and the NAM sugar molecule, which is new in this lesson video. And so the nag recall is just an abbreviation for n acetyl glucosamine, and the name, on the other hand, is an abbreviation for n acetyl Muir Amick acid. So N. A M now in potato blight can structure the nag, and the NAM sugar units are going to be co violently linked to each other via these beta 14 Glick acidic languages. And of course, we have another beta configuration in the Glick Acidic Linkage, which reminds us that the function is once again going to be a structural function. And so in our next lesson video, we'll talk about how Pep Tito Blake can is the main structural component of bacterial cell walls. And so, of course, the organism is going to be bacteria. Now, in terms of being a branched Polly Sacha ride, we can say that Pep Tito Bleich hand is not going to be branch. So no branches and Pep Tito Glikin. Now, you might be wondering about the prefix pep Tito that we see in Pep Tito Blake. And it kind of sounds like a peptide, which is a protein. But I thought Pep Tito Glikin was a carbohydrate, not a protein. So why this Pep Tito prefix? Well, it turns out that in Pep, Tito, Blake and structure, there actually is a short peptide cross linking the poly Sacha ride, uh, structures. And so that is exactly where the pep Tito prefix comes from. And so notice if we take a look at our image over here, we're showing you Pep, Tito, black and structure notice that this and this are the, uh, Polly Sacha right portion. So the carbohydrate portions and then notice down below. Uh, these linking structures are the peptide cross links, so you can see the pink highlights represent the poly sack ride and these green highlights that you see, uh, beneath here are all going to be peptide cross links. And so, if we take a look at the poly Sacha ride portion, which is again, this highlighted, uh, pink portion here. If we zoom in on this little region right here and blow it up in this image, you'll note that the sugar units are nag nag molecules, which again are the same exact sugar molecule that we talked about in the chitin topic. And then we also have over here the Nam, the NAM Sugar unit, which is, of course, and a Seattle Muir Amick acid. And so you'll note that, uh, Nam, uh, still has an amino sugar here. But it also has, uh, this region over here, which would be a carb oxalic acid, uh, if it weren't connected to the peptide link down below. And so that's what makes this, uh, this group right here, highlighted in yellow is really what distinguishes Nam from nag. But really, the main take away is just to know, uh, Nag and Nam are gonna be linked together in Pep Tito, black hand structure and of course, the linkage is going to be a beta like acidic linkage. As we can see here, the two carbon atoms are one and four. And so, really, this concludes our introduction to Petito Glick hand structure. And in our next lesson video, we'll talk about the differences between gram positive and gram negative bacteria. So I'll see you guys in that video.

So in our last lesson video, we said that Petito Glicken is a structural Polly sack right that makes up the structures of bacterial cell walls. And so that leads us to two different categories of bacteria. Gram positive bacteria and gram negative bacteria. And so bacteria can be categorized based on whether or not they absorb the gram stain. And so we're not going to get into the details of the procedure of the gram stain in this video. But what you guys should know is that Gram positive bacteria are going to react positively to the gram stain, and so that means that they're going to absorb the gram stain. However, Gram negative bacteria, on the other hand, are going to react negatively to the grandstand, which means that they do not absorb the gram stain. Now, in terms of their structures, we can say that gram positive bacteria, uh, they have their cell membrane surrounded by just a thick cell wall made up of pep, Tito Glick hand and just for context. In comparison, this thick cell wall is about 250 Angstrom is thick and again, this is not a number that you guys need to memorize. It's just for comparison purposes to the gram. Negative bacteria. And so I noticed that the gram negative bacteria have their cell membrane surrounded by more than just a thick cell wall there, surrounded by both a thin cell wall and another complex outer membrane. And so the thin cell wall of gram negative bacteria just for context is only about 30 Angstrom stick, which is about eight times less thick than the cell wall of gram positive bacteria. And so what's important to note about the gram negative bacteria? Is that the outer membrane this complex out, remembering that they have, well, actually make the gram negative bacteria mawr resistant to some antibiotics. And so that's something important to keep in mind. All right, so if we take a look at our image down below over here on the left hand side, notice that we're showing you gram positive bacteria. And so over here we have our grand, positive bacterial cell. And if we take a little cross section of the perimeter of our grand positive bacterial cell and pull that out over here and then zoom into this little cross section, which will finds that The perimeter of the grand positive bacterial cell consists of a cell membrane here in blue and a thick pep Tito glide can cell wall and so again, weaken right over here that this is a thick pep Tito black and wall that is about 250 angstrom thick. Now, over here on the right hand side, we're showing you gram negative bacteria. And so over here we have our gram negative bacterial cell. And if we take a little cross section of the perimeter of the gram negative bacterial cell and pull it out and then zoom into that cross section, you'll find that there's actually a very thin layer of Pep Tito Glikin. And so there's a thin pep Tito Blake and cell wall that's Onley. About 30 angstrom is thick, and then you can see that this thin petito, Blake and wall here is actually surrounded by ah membrane down below, which is gonna be the inner membrane, and it's also surrounded by another membrane. Up above that is going to be the outer membrane and notice that the outer membrane is more complex with these lipo polly sacha rides that are attached to it. which are just Polly Sacha rides with lipids attached. And really, it's this complex outer membrane that allows gram negative bacteria to beam or resistant to some antibiotics. Now what helps me remember the differences between gram positive and gram negative bacteria is that when I think about the positive, I think about the positive sign. And, of course, when I think about negative, I think about the negative sign and so note that the positive sign is actually quite thick, especially in comparison to the negative sign, which is quite thin. And so this helps me remember that it's the gram positive that have a thick pep Tito glide cancel wall and the gram negative that have a thin pep Tito glide cancel wall. And then, of course, the gram negative bacteria is gonna need to compensate for having a thin pep Tito glide cancel wall by having a mawr complex outer membrane. And so, hopefully this will help you guys remember the differences between gram positive and gram negative bacteria. And that concludes this video. So I'll see you guys in our next one

What type of molecule provides the 'cross-links' between the peptidoglycan polysaccharides?

• A. Fatty acid.
• B. Lipid.
• C. Carbohydrate.
• D. Protein.
• E. Salt bridge.

Which of the following best describes the structure of the Gram-negative cell wall?

• A. A thin layer of chitin with an outer membrane on top.
• B. A thin peptidoglycan layer between two cell membranes.
• C. A thick peptidoglycan layer with an outer membrane on top.
• D. A thick peptidoglycan later under an outer membrane.