How is starch digested?

Answer 1

While structurally different, the two forms of starch—amylose (linear) and amylopectin (highly-branched)—are broken down by many of the same enzymes. The process of digestion begins in the mouth. Salivary ?-amylase hydrolyzes the ?-1,4 glycosidic bonds in both amylose and amylopectin, yielding smaller chains called dextrins. Dextrins pass unchanged from the stomach into the small intestine (acidic environment of stomach stops the enzymatic activity). Pancreatic ?-amylase found in the small intestine hydrolyzes ?-1,4 glycosidic bonds, breaking dextrins down into the disaccharide maltose. Maltase, an enzyme found in the brush border of the small intestine, breaks down maltose into glucose. Because amylopectin contains ?-1,6 glycosidic bonds, an additional step is required. Another brush border enzyme, ?-dextrinase, is needed to hydrolyze the bond to complete the digestion of amylopectin. The glucose molecules are now ready to be transported into the enterocytes.