9. How are polysaccharides and disaccharides digested?
The process of digestion of carbohydrates occurs in the mouth and small intestine.
Digestion of carbohydrates in the mouth- After entering into the mouth, the food gets mixed with saliva which breaks down the starch into maltose, isomaltose and limit dextrins. Saliva contains an enzyme called salivary amylase which is involved in the break down of starch into its constituents at a particular pH of 6.8. This enzyme continues to act in the oesophagus, but its action stops in the stomach as the contents become acidic. Therefore, the carbohydrate-digestion stops in the stomach.
Digestion in the small intestine- In the small intestine, carbohydrate digestion resumes. The food is acted upon by pancreatic juice and the intestinal juice. Pancreatic juice contains the pancreatic amylase that hydrolyses the polysaccharides into disaccharides. On the other hand, intestinal juice contains a variety of enzymes (disaccharidases such as maltase, lactase, sucrase, etc.) which help in the digestion of disaccharides.
The digestion of carbohydrates is completed in the small intestine.