9. Carbohydrates
Disaccharides
1
concept
Disaccharides
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in this video, we're going to introduce some specific dye sacha rides and so recall that die Sacha rides are defined as sugars that consists of exactly two mono sacha rides that air co violently linked together by an OGE like ascetic bond. And so the prefix die means to. And of course, Sacha rides means sugars. And so there are many, many, many die sacha rides that exist in nature, So you're definitely not expected to memorize all of the dice. Ackroyd's but the most abundant die sacha rides are the following four that we have listed, which arm all toas selo bios, lactose and sucrose. And so notice down below in our image here we're just giving you information about these four die sacha rides and, of course, the dice. Ackroyd consists of a sugar one plus a sugar to AIG like acidic linkage that is linking those two sugars. And so, in this table we have sugar one here in the first row, sugar to here in the second and the black acidic linkage here in the third. And then we'll put the name of the dice, aka right here in this column give you a little bit of information about the dice, aka right and then let you know if the died sack right is digestible or not with these check boxes, and then also noticed that the table that you see up above here is color coordinated to the structures of the dissect rides that you see down below. So the yellow corresponds with the yellow green corresponds with the green, the white corresponds with white. And, of course, the blue here corresponds with the blue. So let's go on and get started here with our first row, which is actually going to be the dye sacha ride mall toes and so notice that maltose is a dice accurate that has both of its sugars identical to each other. And so it consists of two D glucose molecules. So if we take a look at what Malta's structure down below noticed that it indeed consists of two D glucose residues and, of course, the Gleick ascetic linkage that's used to link together these two D glucose residues. Aziz identified here in this image is an Alfa 14 Gleick ascetic linkage. Now as well. See, moving forward in our course mall toes is a dice aka Ride that we're going to find can be found in the Pali Sack, right, called starch. And again, we'll talk more about the starch Polly Sack ride later in our course. But it's important to start associating mall toes with Start. And, of course, starches are found in many plant based foods, including potatoes. And so, of course, mall toes and starches are going to be digestible, so we could go ahead and give this box a green check marks. Since mall toes is digestible now, the next row that we have here is the Di Sacha ride Celo bios. And so what you'll notice about Celo bios is that it also consists of the same exact sugar residues as maltose. It consists of two D glucose residues, and so, if you take a look down below at our image of celeb bios, again, notice that it consists of two D glucose residues, just like mall toes. And so the real difference between Maltose and sell a bios is actually the glucose acidic linkage. And so, instead of having an Alfa 14 Glick acidic linkage, Selo bios is actually going toe have a beta 14 Glick acidic linkage. Now, Celo bios, as you can see from its name, is actually gonna be a dice accurate that's found in the Pali Sacha ride cellulose so you can see it's got these same prefixes here, and cellulose again is a poly sacha, right that we'll talk more about later in our course, but important to start associating celo bios and cellulose. Now, interestingly enough, even though mall toes and celo bios on Lee differ literally in the configuration of the an America carbon in the Glock acidic language mall toes is digestible. But Celo bios is actually not digestible by most mammals. And so, of course, what this means is that the configuration of the Glick ascetic bond can actually make a big big difference because it can determine whether or not the dice accurate will be digestible or not. And so that is the main take away here with this digestibility that configurations actually matter now moving on to our third row here. What we have is the dice, aka ride lack toas, and so notice that lack toes will actually swap out the D glucose residue with another residue D galactus dose. And so, if you take a look down below at the lacto structure. Notice that it swaps its first residue here, um, with a galactus uh, sugar. However, the second sugar is still a d glucose sugar, just like all of the other ones that we've covered so far. And also noticed that the Glick ascetic linkage that's used to link together the two sugars in lactose is a beta 14 Glick acidic linkage, just like celo bios had a beta 14 Gleick acidic language. And so what's interesting to point out here is that the beta 14 Gleick acidic linkages can be shown in different ways. So notice that Celo bios has a bit of 14 like acidic linkage. And it seems to be having one sugar above, uh, the other sugar, whereas lactose has a beta 14 Gleick acidic linkages. Well, but the two sugars seem to be perfectly aligned. And that's because of the curvature here that you see with the, uh, beta 14 Gleick acidic linkage. So, uh, it's possible to show beta 14 Gleick acidic linkages with this curvature. Or you could just show it straight up and down like this. So you will see it both ways in your textbooks and both ways, um, in your practice problems now, one thing to note about lack toes here is that lactose is a dice accurate that's commonly found in milk. And so, of course, we know that for most mammals, milk is definitely going to be digestible, so we could go and give it a green check mark. Now, of course, there are some people that are lactose intolerant, and so they can't really digest lactose or milk very well. But that's a special case that we'll talk about later in our course. For the most part, lactose and milk are digestible by most mammals. So now moving on to our fourth and final dice, aka Ride, we have the dice, aka Ride sucrose. Now notice that sucrose keeps the D glucose residue for its first sugar. But instead of swapping out the first sugar again, it's going to swap out the second sugar. And so it uses a deep fryer Arab tose sugar as its second sugar. So if you take a look down below at sucrose structure over here, notice the first residue is still D glucose, just like the one here and the ones over here. But notice that it's actually swapping out the second sugar with a D fruit toast molecule. Now, the Glick ascetic linkage and sucrose structure is actually the most complicated because it includes two and mayor carbons in its like ascetic linkage. And so the first and, um, Eric Carbon has an Alfa one like acidic linkage. But the second and America carbon notice is it's going down on the same side of its highest numbered carbon. So it's gonna have a beta 14 Glick acidic. Oh, I'm sorry. It's gonna be a beta 12 leg acidic linkage because of the second carbon here. And so really, what you'll see is that sucrose is a dice act right that's found in a lot of processed foods, so you'll find it in lots of your cereals and milk shakes and things like that. And so, of course, that means that sucrose is going to be digestible by most mammals. And so this is quite a lot of information to remember about these four die sacha rides. But if you look for very specific patterns, then there's not that much that you really need to memorize and so notice that most of the sugars that we see on this list are actually D glucose residues. And so the only ones that aren't d glucose residues are the D galactus and lactose and the D fructose and sucrose, and then also noticed that for the Glick acidic linkages that all of them are 14 Glick acidic linkages except for sucrose, is a one to like acidic linkage. And then, of course, you'll notice that maltose is Alfa, whereas celo bios and lactose are beta and then sucrose is a combination of both Alfa and beta and then the Onley sugar. Uh, the only dice accurate that is not digestible on this list is, of course, Celo bios. And so just spending a little bit of time looking at this table and trying to commit these structures on components of the structures to memory. You guys will be able to get this down in no time. And so moving forward, we'll be able to get some practice applying these concepts that we've learned. So I'll see you guys in our next video
2
Problem
ProblemWhich of the following contains galactose as one of the sugar subunits?
A
Glucose.
B
Ribose.
C
Maltose.
D
Lactose.
E
Cellobiose.
3
Problem
ProblemWhich disaccharide forms a 1,1-glycosidic linkage?
A
Lactose.
B
Trehalose.
C
Maltose.
D
Sucrose.
4
Problem
ProblemWhat is the identity of the disaccharide below?
A
Cellulose.
B
Lactose.
C
Chitin.
D
Maltose.
E
Sucrose.
F
Cellobiose.
G
Glycogen.
5
Problem
ProblemThe structure of a disaccharide is shown below. Which statement applies?
A
Both sugar rings A and B are in equilibrium with their linear chain forms.
B
Only sugar ring A is in equilibrium with its linear chain form.
C
Only sugar ring B is in equilibrium with its linear chain form.
D
Neither sugar ring is in equilibrium with their linear chain form.
E
None of the above statements are correct.
6
Problem
ProblemName each monosaccharide unit & the glycosidic linkage in the following disaccharide (gentiobiulose).
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7
Problem
ProblemGiven the following information, draw a Haworth projection for the disaccharide gentibiose:
1. Gentibiose is a dimer of glucopyranoses.
2. The glycosidic linkage is β(1 → 6).
3. The anomeric carbon not involved in the glycosidic linkage is in the α configuration.
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