Starch and glycogen are broken down into glucose by amylase and maltase. Digestion of carbohydrates is performed by several enzymes. The steps in carbohydrate digestion are summarized in Figure 15.16 and Table 15.5.
The monosaccharides are transported across the intestinal epithelium into the bloodstream to be transported to the different cells in the body. The monosaccharides (glucose) thus produced are absorbed and then can be used in metabolic pathways to harness energy. Sucrase breaks down sucrose (or “table sugar”) into glucose and fructose, and lactase breaks down lactose (or “milk sugar”) into glucose and galactose. Other disaccharides, such as sucrose and lactose are broken down by sucrase and lactase, respectively. Maltase breaks down maltose into glucose. , sucrases, and lactases, which are also present in the brush border of the small intestinal wall. The disaccharides are broken down into monosaccharides by enzymes called maltases Pancreatic juices also contain amylase, which continues the breakdown of starch and glycogen into maltose, a disaccharide. Recall that the chyme from the stomach enters the duodenum and mixes with the digestive secretion from the pancreas, liver, and gallbladder. The next step of carbohydrate digestion takes place in the duodenum. The acidic environment in the stomach stops the action of the amylase enzyme. The esophagus produces no digestive enzymes but does produce mucous for lubrication. As the bolus of food travels through the esophagus to the stomach, no significant digestion of carbohydrates takes place. The salivary enzyme amylase begins the breakdown of food starches into maltose, a disaccharide.
The digestion of carbohydrates begins in the mouth.
0 kommentar(er)
