Glycoconjugates - Video Tutorials & Practice Problems
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Glycoconjugates
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Alright. So in this video, we're going to introduce glyco conjugates. So what exactly are glyoconjugates? Well, glyconjugates are just oligosaccharides or small sugars that are conjugated or covalently linked to another chemical species that is not a carbohydrate. So for instance, either a lipid or a protein. And so if we take a look at our image down below over here on the left hand side, notice that this blue structure that we see here is definitely a carbohydrate. And so this is what the glyco prefix is referring to in glyoconjugates. But then notice that this carbohydrate is covalent attached to this y group over here and we're defining this y group as just a non carbohydrate molecule. So it's anything but a carbohydrate. So for instance, it could be a lipid or it could be a protein. And so this y group is what the conjugate portion of the word glyconjugate is referring to. Now, the oligosaccharide portions of glyconjugates are very heterogeneous. And so by heterogeneous, what we mean is that they're made up of more than one type of sugar. And so if we take a look down below at this oligosaccharide, notice that we have more than one type of sugar in there. We've got some green ones. We've got some blue ones in here and we've got red and other colors as well. And so you can see that we have different types of sugars in the oligosaccharide portions. And so if this were instead of heterogeneous, if it were homogeneous, what that would mean is that all of them, the homo part means all the same. And so this means that all of these would be like a green color for instance because they were all the same. But, again, the oligosaccharide portions are not homogeneous, they are heterogeneous, meaning different sugars. Now, it's also important to note that oligosaccharides, they have the ability, so they can show directionality. Of the oligosaccharide that is chemically of the oligosaccharide that is chemically different than the other end. And so, this can be done with having a non reducing end on one end of the oligosaccharide and a reducing end on the other end of the oligosaccharide. And so if we zoom in, on this region of the oligosaccharide down below here, notice that this end of the oligosaccharide, does not have a free anomeric carbon. In fact, this is not an anomeric carbon because it's only bonded to 1 oxygen atom and anomeric carbons are always bonded to 2 oxygen oligosaccharide, Now on the other hand, if we zoom in on this end of the oligosaccharide over here, notice that on this end we do have an anomeric carbon that is bonded to 2 oxygen atoms, the ring oxygen and the hydroxyl group oxygen. And so this anomeric carbon is a free anomeric carbon forming a hemiacetal group and so that makes it a reducing end. And so, you can see that there is some directionality here, there's the non reducing end of the sugar and then there is the reducing end of the sugar. And so as we move forward in our course, we're gonna talk about 2 very specific types of glyoconjugates, Glycolipids and Glycoproteins. So I'll see you guys in our next video.
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Glycoconjugates
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So in this video, we're going to introduce the simple idea of a glycolipid. And so a glycolipid is just a hybrid molecule. So, it's a combination of 2 different types of molecules. The first is going to be a lipid molecule and the second is going to be, carbohydrates or small sugars. And so Glyco, is the prefix referring to sugars and of course, lipids are referring to lipids. And so glycolipids are hybrid molecules made up of lipids, covalently linked or covalently attached to small sugars. And so if we take a look at our image down below, notice that we do have this oligosaccharide right here and notice that the oligosaccharide is quite heterogeneous, so it's made up of many different types of, monosaccharide units. And notice that the oligosaccharide is covalently attached to a lipid here and that is what makes, this glycolipid. And so, we will be talking more about glycolipids throughout our course especially when we're talking about bio signaling later in our course. And, we will also talk a lot more about lipids later in our course when we're focusing on lipids as well. But for now, this is the conclusion to our simple idea of glycolipids and, we will see you in our next video when we talk about glycoproteins.
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Glycoconjugates
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In this video, we're going to introduce the relatively simple idea of a glycoprotein and so you may have already guessed, but a glycoprotein is just another hybrid molecule so it's a combination of 2 molecules. It's made up mostly of a protein and that protein is going to be covalently linked to a relatively small oligos accharide or a relatively small sugar. And so if we take a look at our image down below over here, notice that this big circle that we see right here represents a protein. And then you can see over here we have an oligosaccharide and our oligosaccharide notice is very heterogeneous, meaning it's made up of many different types of sugar units. And then if we covalently attach the protein to the oligosaccharide, we can get this structure over here which is the glycoprotein. Now, glycoproteins as we'll see moving forward throughout our course, they're gonna be found inside of cells. They'll be found on the outside of cells in the extracellular matrix and on the outer surface of the plasma membranes of cells as well. Now, it turns out that antibodies are actually glycoproteins as well. And so notice over here on the far left, we have the same image of antibodies that we had in our previous lesson video. So notice that what we have here is identical. And so really the only thing that's different between this image that you see here and, the image that we had in our previous lesson videos is, this region that's coming off here from the, the stem of the antibody. And so notice that these are oligosaccharides coming off of the stem. And so, the oligosaccharides can also help to create a lot of diversity with the antibodies and that can also help change their functions and whatnot as well. And again, we'll be talking about glyconjugates like glycolipids and glycoproteins throughout our course. So it's good to get these introductions out of the way. And so in our next video, we're gonna talk about how, exactly are proteins linked to the oligosaccharide, portions. And so I'll see you guys in that next video.
4
concept
Glycoconjugates
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In this video, we're going to distinguish between o linked and n linked glycoproteins. And so really, we're just gonna talk about the idea of how exactly are the oligosaccharide portions of glycoproteins linked to their proteins. And so it's important to note that glycoproteins will form glycosidic bonds between a sugar's and an americ carbon and the amino acid residues are group and not the amino acids backbone. And so really the oligosaccharide portion of a glycoprotein can be linked to the protein in one of 2 ways. The first way is through an o linked glycosidic linkage and the second way is through an n linked glycosidic linkage. Now the o linked glycosidic linkage is gonna form with the oxygen atom of a hydroxyl group of either a serine or a threonine amino acid residues r group, And of course the n link like acidic linkage is gonna form with an amide nitrogen atom of an asparagine amino acid residues r group. And so if we take a look at our image down below over here on the left hand side, notice that we're showing you O linked glycoproteins. Notice that we have a carbohydrate right here and its anomeric carbon is right here forming a covalent bond with the oxygen atom of a serine's r group. And notice over here we have another carbohydrate whose anomeric carbon again is forming a covalent linkage with the oxygen atom of the r group of a threonine amino acid residue. And so again, this is just, one of 2, these are 2, potential ways that carbohydrates can be linked to their proteins through o glyca, o linked glycosidic linkages. Now notice over here on the far right, we're showing you n linked glycoprotein and so we can we have our carbohydrate right here and notice that its anomeric carbon is forming a covalent bond with the nitrogen atom of the amide that's present in asparagine's r group. And so again, the main takeaway here is that the carbohydrates, that are found in glycoproteins are going to be linked to the proteins via the r groups of either a serine or a threonine amino acid residues R group, using an o linked glycosidic linkage or through the r group of an aspair gene amino acid residue, with an n linked, glycosidic linkage. And so, this here concludes our lesson on the difference between o linked and n linked glycoproteins. And as we move forward in our course, we'll be able to apply some of our practice problems. So I'll see you guys in our next video.