Label & name every glycosidic bond in the branched oligosa...

Question

Label & name every glycosidic bond in the branched oligosaccharide below:

Accepted Answer

Alright. So this practice problem wants us to label and name every glycosidic bond in the branched oligosaccharide down below right here which notice has a total of 6 sugar units. And so of course, if we want to label and name every glycosidic bond, we're first gonna need to be able to identify where these glycosidic bonds are. And so let's go ahead and highlight the glycosidic bonds. So notice that we have one here, we've got one here, we've got one here, we've also got one here, and we've got one over here as well. And so what you'll notice is that the glycosidic bonds that are highlighted in yellow look very very similar to each other, whereas, the glycosidic bond here in blue and the one over here in green look a little bit different. So, we're gonna start with the glycosidic bond here in yellow. Now we know from our previous lesson videos that when it comes to naming glycosidic bonds, that the anomeric carbon is going to be very key. And so let's go ahead and identify the anomeric carbon for each of these six sugar units. Recall that the anomeric carbon is the only carbon atom that's gonna be bonded to 2 oxygen atoms. And so this is an anomeric carbon. So is this one. So is this one. So is this 1. This is an anomeric carbon and so is this one right here and so these are the 6 anomeric carbons circled in red for each of these 6 sugar units. And of course, we know that when we're numbering the antimeric carbons, we want them to have the lowest possible number. And so focusing here on, the the bonds highlighted in yellow, notice that, the lowest number for these antimeric carbons is gonna be number 1. For these sugars here. And so, of course, that means that when we're looking at this sugar unit over here on the far left, that this carbon atom is going to be carbon 6, the highest numbered carbon and so, notice that with this, again, yellow background, glycosidic bond that the glycosidic bond itself is actually going in somewhat of a downwards direction. It's going downwards in the opposite direction of the highest numbered carbon. And so that means that it's reaching down for the ants and this is going to be an alpha configuration. And so, of course, this is the only anomeric carbon involved in this glycosidic bond. So it's just going to be, the alpha here that we need to consider, so we can write alpha below it. And, of course, this is an alpha one so far. And then, we need to figure out what is the number of this carbon over here. So we already identified, this anti magnetic carbon as number 1 over here. So this would be number 2. This would be number 3, and then this one here would be number 4. And so what you'll notice is that this is, this glycosidic linkage here is an alpha one 4 glycosidic linkage. So an alpha 1 comma 4 glycosidic linkage is this yellow one right here. And, okay. So now we can move on to this yellow one over here and notice again that, for this sugar unit right here, if we continue the numbering, this is 4, this carbon here would be 5, and this carbon here would be 6. Notice that the glycosidic, bond here on the anomeric carbon is going again in somewhat of a downwards direction, in the opposite direction of the highest numbered carbon. And so again, we have another alpha configuration here, so we can go ahead and write alpha here. And this is an alpha one because of the one here, so alpha 1. And so now we need to determine the, numbering of this carbon atom over here. And so, when we take a look at, this being the anomeric carbon, this will be assigned carbon number 1. And then of course this would be 2, this would be 3, this carbon atom would be 4. And so, of course what we see is that we've got another 14 glycosidic linkage. Alpha 14. And so, this yellow one here matches, this yellow one and this yellow one are matching. So, let's go up and do this one too, which seems to be very similar. And so again, we've this is carbon number 1. That means that this is gonna be carbon 2, carbon 3, carbon 4, carbon 5, and carbon 6. And so notice again that here we have the anomeric carbon, the glycosidic bond seems to be pointing in a downwards direction in the opposite direction of the highest numbered carbon, which again tells us that this is another alpha configuration here for this anomeric carbon. So, it's on the carbon number 1, so we have another alpha 1. And then we need to determine the numbering for this carbon atom and, we already identified this one as the anomeric carbon, so the lowest number here is 1. This is gonna be 2, this will be 3, this carbon atom will be 4. So it looks like we have another alpha 14glycosidic linkage here. Alpha 14 for this yellow one. So now, we're done with all of these, glycosidic linkages with yellow background. So we can move on to the last, 2 here which are this one in blue and this one over here in green. So let's start with the one in blue and notice that we have, the anomeric carbon here is 1. And, if we continue the numbering system, this is carbon 4. That means that this one will be carbon 5. This will be carbon 6. Notice that the glycosidic bond here on the anomeric carbon is going in a downwards direction and the opposite direction of the highest numbered carbon. And so that means that this is going to be an alpha configuration. And so, what you'll notice is that, we need to determine the number of this carbon atom. And so here in this sugar unit, we already have the numbering system going. So we have, 1, 2, 3, 4. That means that this one would be 5 and this one up here would be 6. And so what we're seeing here is that this is going to be an alpha 16. So this will be an alpha 16 glycosidic linkage right here. And so, now we're done with this one. We can move on to our final glycosidic linkage, this green one over here. And, again, notice that the anomeric carbon seems to be actually going in an upwards direction here. The glycosidic bond seems to be going in an upwards direction in the same direction as its highest numbered carbon. They're both going up. And so when they're going in the same direction, we think about the bumps of the beta being on the same side. And so that means that this is going to have this anime carbon will have a beta configuration. And so it's, of course, it's gonna be beta 1, because it's on the, first carbon here. And so we need to figure out the numbering of this carbon. And so, this one we've identified as the anomeric carbon, so this will be carbon 1, this will be carbon 2, this is carbon 3, and then of course this is gonna be carbon 4. And so what we can see here is that we have a beta 14glycosidic linkage here in green. So we can do a beta 14, and we can highlight this green linkage here as a beta 14. And so really this is it for our practice problem. We've got a total of 5 glycosidic linkages. The ones in, yellow here are alpha 14glycosidic linkages. The one in blue is an alpha 16glycosidic linkage and the one in green is a beta 14glycosidic linkage. And so that concludes this practice problem and I'll see you guys in our next video.

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Label & name every glycosidic bond in the branched oligosaccharide below:

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