Digestion of Carbohydrates:
The purpose of carbohydrate digestion is to break down and hydrolyze the di and polysaccharides of the diet to their basic simple sugars. This process is accomplished by enzymes of the digestive juices and gives several end products. Salivary amylase starts the digestion of cooked starch in the mouth. But very little digestion takes place in the mouth since the food remains in the mouth for a very short period of time.
Although some hydrolysis of starch to maltose occurs in the mouth by the action of salivary amylase and continues in the stomach until the food mass is acidified. The principal site of digestion of carbohydrates is in the small intestines. It doesn’t act upon raw starch. But pancreatic amylase breaks down both raw and cooked starch to dextrin and in turn, to maltose. Cooked starch is more rapidly hydrolyzed because the cell walls have been ruptured and the enzymes have more ready access to the starch granules.
Absorption of Carbohydrates:
The monosaccharides are absorbed into the mucosal cells of small intestines and pass into circulation via the portal vein. The microvilli (brush border) lining the mucosa cells greatly help the absorption by increasing the surface area. The first organ to receive glucose, fructose, and galactose is the liver. The liver takes them up and converts galactose to glucose. It breaks fructose into even smaller carbon-containing units and either store’s glucose as glycogen or exports it back to the blood. How much glucose the liver exports to the blood is under hormonal control.