Final answer:
Amylase cannot break down carbohydrates in the stomach because the acidic environment deactivates the enzyme, and necessary carbohydrate-digesting enzymes are absent in the stomach's gastric secretions. Carbohydrate digestion resumes in the duodenum with the help of pancreatic juices.
Step-by-step explanation:
Amylase cannot break down carbohydrates in the stomach because the acidic environment in the stomach inactivates the enzyme. The digestion of carbohydrates begins in the mouth where salivary amylase starts the breakdown of starches into maltose. This enzyme is optimized to work at a neutral or slightly alkaline pH, specifically around pH 6.9, which is found in the mouth. As the food bolus moves to the stomach, the highly acidic pH due to hydrochloric acid (HCl) in the stomach rapidly deactivates amylase. Pepsin, an enzyme in the stomach, further hydrolyzes and deactivates amylase, which stops the carbohydrate digestion process in the stomach.
Furthermore, the enzymes needed for the digestion of carbohydrates, such as sucrase, lactase, and additional amylase, are not present in the gastric secretions. Carbohydrate digestion resumes in the duodenum, where pancreatic juices containing amylase, secreted by the pancreas, continue the process of breaking down starch and glycogen into disaccharides and ultimately into monosaccharides like glucose for absorption into the bloodstream.