Hello everyone. Week two, and this is the third session of week two. In the previous session, I hope we clearly understood how we can feel hunger and how active feeding behavior can be developed. And then you can imagine, we just consumed a lot of food. And from now on, I'm about to introduce the bioenergetics in particular by focusing on carbohydrate digestion. So today's topic is carbohydrate digestion. So in the beginning, we have to review what a carbohydrate is. So, carbohydrates. So general chemical formula is Cx(H20)x the number wise. Why is that carbohydrate? Carbon. Carbon is hydrated, so hydrated carbon. One good example is glucose. Glucose is the most important source of carbohydrate for your body from corns and rice. And you're looking at the structure, the linear form of glucose or lean form of glucose. So chemical formula is based on this. We could just write it down, C(6) H(12) O(6). Six Carbons containing hydrated molecule, glucose. So this glucose can be stored in our liver and in our muscle in the form of glycogen. I'm going to show the structure of glycogen in a minute. So, what types of carbohydrates are available? So we have to go through the structural aspect of carbohydrate. So, saccharide means sugar. Depending on the number of building block. Mono means number wise one. Monosaccharide means just one simple sugar molecule. Oligosaccharide means several building blocks like sugars are polymerized. And lastly, polysaccharide means many, several thousand and more than that. Many, many, many monosaccharides are linked throughout covalent bonds so-called glycosidic bond. You're looking at over here, glucose molecules, these monosaccharides are there linked throughout these covalent bond and these bond is the so-called glycosidic bond. So starch, and glycogen, and cellulose those small dots indicate glucose. They are being polymerized throughout those covalent glycosidic bonds. Sometimes branched, sometimes just linearized and very heavily and tightly packed to each other and they can form different types of glucose polymers, Polysaccharides. In terms of Monosoccharides, obviously glucose. Six carbon containing carbohydrates, the other one is fructose and galactose. Fructose has how many carbons? One, two, three, four, five, six. But structure is more like pentagonal. And galactose a very close to glucose. So the reason I showed this Monosaccharide for you is to introduce the disaccharide structure. When glucose and fructose, they are linked by glycosidic bond, when those two sugars are linked in the form a disaccharide, that means this is sucrose. And when two glucose molecules are linked, in that case that sugar is called maltose. And when glucose and galactose they're linked, that disaccharide is called lactose. Probably those words: lactose, maltose, sucrose, you probably are very familiar with those different types of sugars. There can be easily found from the food labels. All right. Let's begin with the digestion. These carbohydrate digestion begins inside your mouth, the first digestive organ in the digestion system. So in particular, there are many glands around you oral cavity. Salivary glands in the mouth secrete saliva. In particular, the enzyme called Amylase. Amylase is the first major enzyme. It can break down the polysaccharide sugar polymer, glucose polymer: starch. All right. So, when glucose, they're polymerized in the form of starch, just imagine, you just had a lot of bread or a bowl of rice. And inside of your saliva there is a amylase concrete that covalent bond. So make these large molecular polysaccharide into smaller pieces. And then, what's next? In your mouth, salivary glands and amylase breakdown carbohydrates. And then, there is no further digestion throughout your esophagus or even stomach. There is no digestion, carbohydrate digestion. So, main side of complete digestion of carbohydrates occurs in your small intestine. And what types of organs and enzymes are involved in this process? In this process means carbohydrate full digestion. So full digestion of carbohydrate occurs inside your small intestine. So, when the chyme, chyme means partially digested food mixture with hydrochloric acid. This is secreted from your stomach and other fluid. When this chyme getting into the duodenum, the beginning of small intestine and that's the kind of signals. And when chyme enters into your duodenum that send the signals, and pancreas release digestive enzyme, pancreatic amylase. So, pancreatic amylase is again, is like your salivary amylase. Its main job is to further degrade the polysaccharide carbohydrate into smaller oligosaccharide. And there are more enzymes, dextrinase, and glucoamylase. You don't need to remember those names of those enzymes, but their job is to hydrolyzed oligosaccharides. And overall, this is the structure of your small intestine. So highly folded up throughout those epithelial cell linings, highly [inaudible] This is called a villi structure and intestinal epithelial cells, general morphology looks like this. In particular, this region is facing the lumen. That means the outside of our body and severe chemical digestion occur. So, the small intestine also produces other enzymes like lactase, or sucrase, and maltase, and those enzymes ultimately break down, let's say, lactose into glucose and galactose. In the case of sucrose, sucrase degrade sucrose into glucose and fructose. In the case of maltase, degrade maltose into two glucose molecules. So my point is, carbohydrates, so polymeric carbohydrates can be chemically degraded into individual monosaccharide. And next step for carbohydrate digestion, is the absorption of these digested monomeric sugar particles inside your body throughout these brush border cell layer. Individual sugars, now fully degraded into monosaccharides, they should be absorbed. That's the topic for next session.
