22.3 Digestion of Carbohydrates Carbohydrates begin digestion in the mouth, proteins in the stomach and small intestine, and lipids in the small intestine. Learning Goal Give the sites and products of the digestion of carbohydrates.

Stage 1: Digestion of Carbohydrates Carbohydrate digestion begins in the mouth, where salivary amylase breaks down polysaccharides into smaller polysaccharides (dextrins), maltose, and some glucose. In the stomach, the partially digested starches enter the acidic environment, where the low pH stops further carbohydrate digestion.

Digestion in Small Intestine In the small intestine where the pH is about 8, enzymes produced in the pancreas hydrolyze the remaining dextrins to maltose and glucose. enzymes produced in the mucosal cells that line the small intestine hydrolyze maltose, lactose, and sucrose. the resulting monosaccharides are absorbed through the intestinal wall into the bloodstream. In the liver, hexoses fructose and galactose are converted to glucose, the primary energy source for muscle contractions, red blood cells, and the brain.

Digestion of Carbohydrates