7. Prokaryotic Cell Structures & Functions
Introduction to Bacterial Cell Walls
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In this video we're going to talk more details about peptidoglycan structure. And so peptidoglycan consists of repeating units of 2 different monosaccharides. And these 2 different monosaccharides are going to be linked to each other covalently by a special type of bond known as a beta 14 glycosidic linkage. And so these 2 different monosaccharides are number 1, n Acetylglucosamine or NAG for short, and N Acetylmuramic acid or NAM for short. And so these nag and nam subunits are going to be repetitively linked together to create a long chain known as a glycan chain. So the glycan chain is really just a sugar chain, made up of repeating units of nag and nam repetitively linked together. And so if we take a look at our image down below on the left hand side over here, we're showing you an image representing peptidoglycan structure. And notice that it consists of multiple glycan chains. So each of these chains is referred to as a glycan chain. So here we're showing you 3 glycan chains right here. And each of those 3 glycan chains consists of repeating nag and nam subunits. So notice that the nag subunits are in blue and the NAM subunit are in green. And notice that the NAG and NAM repetitively are gonna be repetitively linked to create these, glycan chains that you see here. And so, in addition to these glycan chains, what you'll notice is that there's also a 4 amino acid chain known as a tetrapeptide. Since tetra is the prefix that means 4, and, because these are amino acids, it's going to be a protein, a small peptide. And so this tetrapeptide is going to be attached to each of the NAM molecules. And so, this tetrapeptide is going to be important for the cell wall structure to give that cell wall extra rigidity. And so if we take a look at our image down below, once again, in addition to these glycan chains, what's linking these glycan chains are these tetrapeptide units that you see here. And so these tetrapeptide units, are going to be very, very important to link adjacent glycan chains together. And so if we take a look at the image over here on the right hand side, notice that it's zooming in to this specific, region right here. And, within this specific region, what you'll be able to notice here is that we have a n Acetylglucosamine molecule right here, and this is again going to be the nag subunit. And we have over here an n Acetylmuramic acid molecule right here, and this is going to be the nam subunit. And so notice that the nag and nam subunits are linked to each other via this bond that you see here. And this bond is what we call a beta 14 glycosidic linkage. Glycosidic linkages are, linkages that will link monosaccharides together. And so, notice that branching off of the NAM subunit is a tetra peptide. And so this tetrapeptide consists of 4 amino acids. And so you can see the tetra peptide is right here. Each of these circles that you see here represents an amino acid. And so, we can call this, these here amino acids forming this tetrapeptide chain. And so, this here concludes our brief introduction to peptidoglycan structure and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
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