1Metabolism 1 Exam 11. What are monosaccharide, disaccharides, oligosaccharides, and polysaccharides? - When people talk about the chemical structure of carbohydrates, they can be classified of mono-, di-, oligo, or polysaccharides. These names differ in the number of individual molecules. When youbreak them down to their simplest form, they are called monosaccharides (mono for one) These are galactose, glucose, and fructose. There are others, but these are the most important. - The disaccharides are when two of these molecules react with water and form a bond together. When two glucoses condensate (combine with water), you get maltose. When a glucose and fructose condensate, you get sucrose. When a glucose and a galactose condensate, you get lactose.- Then when 3-10 of these monosaccharides combine, you get an oligosaccharide. Oligo- means a multiple of. - Polysaccharides are many of these monosaccharides; mainly glucose molecules. This is how energyis stored, and they are either called starch (energy form in plants) or glycogen (energy form in animals). 2. What are the other parts that we need to know for carbohydrate structure?- Glucose is the most abundant monosaccharide. In the blood, all circulating carbohydrates are glucose. When two monosaccharides combine with a water molecule, you will get a disaccharide. The oligosaccharides are either linked by alpha 1-4 or beta 1-4 bonds (1 and 4 referring to the carbon that binds them together. The body lacks the enzyme to break the beta bonds. This is what fiber is made from; beta bonds. Know the two types of beta linkages for the test. They are raffinose and stachynose- Polysaccharides are either classified as starch or glycogen, depending if it is in plants or animals. Then these are also classified as amylose or amylopectin. Amylose is made of all alpha 1-4 bonds. If you look at a structure of glucose, carbon 1 is linked to carbon 4 of the adjacent glucose, so the combined structure is linear.Tony Berardi2 Amylopectin is a combination of alpha 1-4 and alpha 1-6 links. So these molecule is a branched chain, when you look at it. Carbon 6 of one glucose combines with carbon 1 of another glucose,and this forms a branch. o Glycogen is amlyopectin, so it is branched. It is stored in the liver and the muscle. - Now to fiber. These contain beta 1-4 linkages which the body lacks the enzyme to digest, so these just pass throughout your digestive tract. Classified as either dietary (found in nature) or as functional fiber (manufactured), and these can either be insoluble or soluble- The insoluble fiber does not dissolve in water (insoluble), so it will decrease food transit time. Meaning the food will stay in your stomach longer. These are ligans, celluloses, and hemicelluloses.- The soluble fiber dissolves in water, so it will increase the time the food moves through the stomach. These are pectins and gums. So since the body lacks the enzyme to break these down, how are they digested? Bacteria in are colon digest them, these bacteria are good at times. This breakdown produces hydrogen, methane, and gas (which is why eating a lot of fiber will give you crazy gas)3. What do you all need to know about carbohydrate digestion from the mouth to the stomach?- The body starts to digest carbohydrates in your mouth with the enzyme salivary amylase. Mastification (chewing) increases the surface area for salivary amylase to act on. Thisrnzyme breaks the bonds in the alpha 1-4 linkages (those linear ones), but not the alpha 1-6 linkages. Oncethe food is swallowed, it slides down a long tube connecting the mouth to the stomach, called the esophagus. NO DIGESTION HAPPENS HERE!- At the end of the esophagus is a sphincter the opens to let food into the stomach and closes to prevent backflow. This is important for two reasons. One being the you don’t regurgitate your food, and two being that the stach is highly acidic and we don’t want that acid to burn our esophagus. When it does backflow, it’s called GERD, or heartburn as we know it. Can be cause by spicy foods, caffeine, and fat. - Then it enters the stomach. The stomach is extremely acidic via HCL (released via gastrin cells). This acid will kill any bacteria and increase digestion of the food further. It inhibits the salivary amylase. HCL is so acidic (pH 2) that it will kill anything, including your stomach walls, if not for themucous that protects the lining of the stomach. Gastrin also releases pepsinogen (anything with the suffix –ogen means it’s the inactive form), which is a protein that breaks down protein. But we aren’t focused on protein right now. Tony Berardi34. Now what happens after the stomach, in the small intestine?- At the bottom of the stomach is the pyloric sphincter, which separates the stomach from the intestine. What was left of the food that you swallowed is called chyme now, after it mixed with the HCL. So what happened all before the small intestine was breakdown of the food, now absorption will happen. That’s the purpose of the small intestine. - The small intestine is divided into the duodenum, the jejunum, and the ileum. The duodenum is where most of the absorption happens. Once in the duodenum, the pancreas releases bicarbonate, which will neutralize that extreme acidity of the entering chyme. Now the shape of the small intestine is a wormlike shape; the surface is highly folded into thousands of small crevices, which are coated with little projection called villi. These projections are covered even more by microvilli, so now the surface area is vastly increased. This is where digestion and absorption happens. The microvilli are just fingerlike projections, and covering these projections are cells called the enterocytes. To make it easier, think of the enterocytes as a waiting room of sorts. This will make sense we cover the nutrient absorption, because the molecules enter the enterocyte, before they enter the body. The villi release enzyme that digest each monosaccharide. The enzymes sucrose, lactase, maltase breakdown their corresponding dissacharides to the 3 monosaccharides. - So to sum it all up: You eat carbohydrates as starch, glycogen, or any of the various forms we went over. Then salvary amylase will start to break down the carbs (via chemical break down). Then it enters the stomach and mixes with HCL, each is acidic enough to kill all bacteria and break the carbs down further. Then the chime will enter the duodenum
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