24. Carbohydrates
Disaccharide
By now you guys should be pro's at monosaccharides, but let's take it a step further and explore what a disaccharide is. In its simplest terms, a disaccharide is two monosaccharides bound by an O-glycosidic linkage (α or β). Below we will take a look at some important ones to remember.
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concept
Disaccharide
7m
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What's up, guys? By now you should know quite a bit about mono sack rides, but in this video, I want to take it a step further and define what a die sack right ISS. So let's get going with that, guys. A die sack right is very simply going to be too mono sack riots that are linked by an OGE like acidic linkage in the middle. Remember that an oak like acidic bond would just be at the an America position, and oxygen a touchtone are. Well, if you have that, where the our group is actually a second sugar that's called the Dia Sack ride. Now it doesn't matter matter whether it's an Alfa linkage or a beta linkage. We'll get more into that in a little bit. That's just going to change the type of guy sack right? It is. But Dice Ackroyd's exists in multiple different forms that are both Alfa and beta cool. So, guys, the exact reaction that brings these two sugars together into one die sack ride is called condensation. And guys. The reason that we call it a condensation reaction is because back when we learned about the definition of condensation What did it always mean? Condensation always means that you take two molecules and you turn them into one bigger molecule. With the release of water, you always have to release one water, Adam or one water molecule to count as a condensation. And that's exactly what happens. And the end product is that we form an ass. It'll linkage. Okay. Remember we talked about a settles. I'm gonna show you guys what the bottle looks like here. Okay, now, one thing that you guys should just keep in mind about dice Ackroyd's is that once you form that die sacha ride, those sugars are locked into position. So the typical type of mutual rotation and epi memorization that might happen when you have a single sugar that cycle eyes is doesn't really happen anymore for die sack ride. So what I'm trying to say here is that once you formed your die sack ride, it's kind of stuck in that position. It's not just going to go from Alfa or Beta and Beta Tau Alfa by itself. Okay, cool. So let's just break down kind of each step of the reaction. Let me explain this diagram to you. So guys. First of all, we need to sugars. So in this case, I decided to bring two molecules of d glucose together toe form a die sack ride. But guys, I could have used pretty much any mono sack rides I wanted. Um, this is just a very common example, and it's a very easy example toe look at, but many different. The multiple forms are multiple types of dice. Ackroyd's exist using different types of sugars and using different types of linkages. So here I'm just giving you an example. So let's say that we wanted to form a beta 14 linkage between these two mono sack rides. Well, what would that even mean? Why would we call it a beta one? Four? Well, guys, first of all, beta always stands for the first sugar and the relationship of the oxygen to the stereo descriptor carbon. So remember guys that this would be my stereo descriptor over here, it's facing up, and in this case, this Ohh, because it's I'm using d glucose. Um, this o h is also facing up. So that means that these air cyst to each other. So this would be beta you guys remember that now it doesn't have to look like this, but this is just the one that we're using for right now. Okay, So this is a beta d glucose and notice that what I'm trying to do is I'm trying to form a linkage between the first carbon of my sugar one and the fourth Carbon of Sugar to and the way that we would count these guys is just like any cyclic sugar. We always count the an americ position as one and then go around in a counter, Aaron in a clockwise way. So then you would get four over here. Does that make sense? So if we were to bring these two alcohol's together, the alcohol on one and the alcohol in four, what we're going to get is the loss of water. And the reason is because if you're trying to make an ass, it'll linkage. All you really need is 10 right. So that means that let's say this is the oh, that stays, Which is okay. Um, actually, that wouldn't be the Oh, that stays. I'm sorry. So let's say this is the old that leaves. Let's say this is the age that leaves. Let's say this is the age that leaves the Oh, that stays. Is this one right? This is the one. And we can go. We'll go through the mechanism later, but that would wind up attaching to the carbon and notice that what we get as a byproduct is 10 and two h is leaving. So we would get the condensation reaction and the release of one water molecule. Okay, so this con, this condensation reaction would then link these two together and notice that what we would now get in terms of this linkage is we would get what we call a beta 14 because once again, the linkages going in the same direction of the stereo descriptor carbon and it's between carbon one of the first one and carbon four of the second one. Okay, now, I noticed that, too Functional groups were present on this die sack ride. One we have in a Seattle. Why do we call this in a Seattle? Because remember, guys that the general formula for a Seattle is that you have O r and oh are connected to the same Cartman. It's like a die either. Is that a die either. Absolutely. This is in a subtle but notice that the an americ position of the other sugar in this case is still exposed. It still has an O. H on it. So that means that in this specific dye sack ride, I would have both an ass. It'll functional group. And ahem, Yes, it'll functional group present on the same molecule. This is going to be important later. But right now I'm just drawing your attention to it. Okay, Now last we have this name of cell you bios so you might be thinking. Well, Johnny, am I supposed to memorize that? Maybe it turns out that some professors and some textbooks and homeworks want you to know some a few of the most important diet sack, right? You don't need to know all of them, but you might need to know a few important ones which I'm going to go ahead and talk about in a second. But for right now, what you should know or what you could just take your take home message from this is that the dye sack ride called sell you bios would specifically be the dye sack right? That's formed from two D glucose molecules making a beta one for linkage. And if you were to change any part of that, it would not be called Sully bios anymore. If you were to make it an Alfa one for linkage, where now it's facing away from the stereo descriptor. Or if you were to change one of the glucose into a fructose, all those changes would have massive impacts on the dice sack ride. It would change the dice Ackroyd completely, and it would also change the name. Okay, so once again, Celia bios is just the example that I'm giving for probably the easiest I sack right to make, which is two d glucose with a beta one for linkage. Okay, so in the next video, what I'm gonna do is I'm going to talk more about important. I Sack writes that you might want to know
Important Disaccharides:
2
Problem
ProblemIdentify the following disaccharides as reducing sugars (RS) or non-reducing sugars (NS)
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3
Problem
ProblemIdentify the following disaccharides as reducing sugars (RS) or non-reducing sugars (NS)
A
maltose = RS; sucrose = RS; lactose NS
B
maltose = RS; sucrose = NS; lactose NS
C
maltose = RS; sucrose = NS; lactose RS
D
maltose = NS; sucrose = RS; lactose NS
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Problem
ProblemDraw a theoretical acid-catalyzed Fischer Glycosidation mechanism for the condensation of D-Glucose into cellubiose. (Note:This reaction would lead to very poor yields of cellubiose- can you hypothesize why?)
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