 This is the last video in this week's collection of videos. We are going to talk about polysaccharides. That's the third type of carbohydrate. Polysaccharides are basically made by taking a bunch of monosaccharides and connecting them to each other in more or less the same way over and over again. This is my cartoon for a polysaccharide. All of these things are largely made of polysaccharides, so cotton. The money that US paper bills are printed on is cotton, although I think they're probably going to go to plastic at some point. Stuff in potatoes is mostly polysaccharide. There's not a whole lot that I'm going to expect you to know about polysaccharides, just a couple of things. There are many different kinds of polysaccharides. Some are made of glucose, which is a monosaccharide. A bunch of glucose is connected to each other over and over again. Some are made of fructose connected to each other over and over again, et cetera, et cetera. Some have one long chain. Other polysaccharides have branches, and I will show you an example of a branch in a little bit. For the most part, the job of polysaccharides is to store energy. In other words, you can get energy from sugar molecules like glucose and fructose, but if you don't need the energy from them, but you've eaten a lot of sugar, one of the things that your body can do is just connect them to each other, make a polysaccharide, and save that. Just save it as stored energy that might be able to be used later. A lot of times, polysaccharides are just used for energy storage. This is just what's shown in this bullet point. When you eat more than enough monosaccharides, in other words, if you eat a lot of sugar and you don't need the extra energy, your body will basically connect a bunch of those monosaccharides together, make a polysaccharide, and shove the polysaccharide in a closet somewhere in the cell and say, maybe I'll need you later. Like I said, there are many different kinds of polysaccharides. I'm just going to show you a parade of polysaccharides. Nothing too crazy going on here. I don't expect you to know a lot of these. There's only one I expect you to know. This is a polysaccharide called amylose. It is connected. It's a bunch of glucose is connected to each other over and over again. This is largely the polysaccharide that's found in things like crackers and potatoes. You don't need to know that one. This is a polysaccharide called amylopectin. This is also glucose is stuck to each other over and over again, but you can see there's a branch here. Amylopectin is commonly found in a lot of fruits. One thing that I should point out, you're connecting a bunch of glucose is over and over again. The way that you connect them is by what? Everybody? That's right, dehydration synthesis. I'm glad you all got that right. This is the one I want you to know. There's a polysaccharide called glycogen. It is the one that humans make and use to store monosaccharides that they might need for later. Because this is the one that humans use, I want you to know that glycogen is a polysaccharide and we humans make it. You don't need to know any of this other stuff. You should know that glycogen is made of glucose monosaccharides, but this you don't need to know. Cellulose, this is the stuff that's in plants, it's in grass and things like that. Glucose is all connected to each other as well, but they're connected in a different way. Because they are connected in a different way, we can eat this stuff, but we can't use it for food. We can't get energy from it because we can't break the attachments. But again, I don't care that you know cellulose. This is just another example. Also made by dehydration synthesis. You can ignore that and ignore all of this. One other thing that I should point out, I said that polysaccharides are often used for energy storage. That's one of the uses. Sometimes polysaccharides can be used to give a hard structure to living things. So for example, you're probably familiar with lobsters and crabs. The shells of lobsters and crabs are made from a special type of polysaccharide that is very tough. Same thing with leaves. Cellulose is one of the things in leaves that makes them relatively stiff and not floppy. That's kind of important if the leaf wants to capture as much sunlight as it can. It needs to kind of be stretched out so that it can catch a lot of sunlight. And cellulose is a polysaccharide that makes the leaf relatively rigid. And that's all I really want you to know. Polysaccharides can be used for energy storage. They can be used as kind of tough structures in living things as well. You should know that there are different kinds of polysaccharides. You should know that we, humans, use glycogen as a polysaccharide. And that's it. So that's it for this week's videos. Bye-bye.