 Hello, today we are going to continue our story about macromolecules, and in specific about polymers, we're talking about carbohydrates, or famously known as carbs. So carbohydrates are polymers whose monomers are monosecarides. I gave here a couple of examples of those monosecarides. Probably the most important one is glucose, and you will see why. Nonetheless, important are fructose, galactose, ribose, deoxyribose. Without these two, there wouldn't be us in the shape that we are. Arbinose, which you are going to practice a little bit in the lab. So you will be familiar with these monosecarides, which are monomers. Now, you have noticed something similar to each of them. So there are some rules that are making life easier in chemistry. If you see something that has O as E as an ending, it's highly likely that it's the case of the simple, of the sugar. And in this case, these are simple sugars that cannot be broken down anymore to make anything that would look like sugar. So glucose, fructose, and so forth. And according to the number of carbon atoms in them, we can recognize several types of the monosecaride. And these are pentose, which have five carbon atoms in them. Hexose having six, heptose having seven carbon atoms in them. And again, you can see O as E, that means it's a sugar. If we think about which of the formula applies to glucose and fructose, we need to see how they are organized in space. So by the number and the type of atoms inside, they both have the same formula, but they are completely differently organized in, have different organized shape. This is critically important, because even the glucose that can have L form and D form, which are like a mirror image. If you have L glucose, it cannot be digested, and that would digest D glucose. So shape is really critically important, okay? Now, sucrose, or table sugar, is made of the glucose and fructose that have bond in between them. De-saccharides, the name says D, or disaccharides, it says two, two sugars. Two glucose sugars are making maltose. Maltose is a de-saccharide, when we're breaking down, when we're eating bread and so forth, starchy food, eventually it goes through the maltose and is broken down to glucose. So glucose is the only component of the maltose as a de-saccharide. Glucose and fructose are components of the sucrose, or table sugar. Interestingly, high fructose corn syrup is actually not completely fructose, but it has higher amount of the fructose than sucrose that it has. And normally it's not found in the nature, it is actually manufactured. Glucose and galactose are forming lactose. I need you to pay attention on that one, because we're going to discuss about the role of the enzymes and the role of the genes and so forth, and we'll mention about lactose. I'm sure that you've heard about lactose intolerance and how some of the products are labeled low or 99% lactose-free and so forth, because not everybody has an enzyme. And the enzyme for lactose is lactase, which is very convenient to remember. We said that OSE as an ending is referring to the sugar, in this case, monosecaride. Desecaride lactose. But ASE refers to enzyme. Which enzyme? Lactase is digesting lactose. So the milk sugar, the sugar that is found normally in milk, is the saccharide that is broken down by the enzyme lactase into galactose and glucose. So when people who have problems with digesting lactose, when they drink buttermilk, for instance, they are completely fine. Because the good bacteria, the bacteria that we use to make that drink, already did that job of breaking down into monomers, galactose and glucose, and make it easy for people to digest that drink. How about polysaccharides? Obviously, poly means many. Examples of the just glucose polymers. So all of these, starch, cellulose and glycogen, have only one monomer. So those are multiples of the glucose. Now, starch is normally built by plants, right? The other use of the glucose that plants are using is actually to build a cell wall. Now, glycogen is the storage of the glucose in both animals in our liver. This is our depot for emergency, for anything that is needed. That's where we are acquiring glucose. And in the mushrooms. When you're eating mushrooms, actually, glycogen is the one that is the storage of the glucose in it. Glucose derivative is chitin, if you remember Lion King. And when Pumba and Timon are saying crunchy, I mean that crunchy part for the bugs actually is due to the exoskeleton, which is consisting of chitin. Interestingly, cell wall that is present in fungus is made of chitin, unlike the cell wall in plants, which is made of cellulose. But all of them are using glucose as a monomer or derivative of glucose in the case of chitin. That would be all about carbohydrates. Thank you.