Describe the digestion of starch in the digestive system: (a) amylase breaks down starch to maltose (b) maltase breaks down maltose to glucose on the membranes of the epithelium lining the small intestine

SouravNovember 14, 2024

Answer

The digestion of starch in the digestive system involves a series of enzymatic reactions that convert this complex carbohydrate into simple sugars. Here’s a detailed overview of the process:

(a) Amylase Breaks Down Starch to Maltose

• Initiation in the Mouth: The digestion of starch begins in the mouth, where salivary amylase (also known as ptyalin) is secreted by the salivary glands. This enzyme starts breaking down starch, which is a polysaccharide composed of glucose units, into smaller molecules, primarily maltose (a disaccharide) and dextrins (shorter chains of glucose).
• Continued Digestion in the Small Intestine: As the partially digested food moves into the small intestine, pancreatic amylase is secreted by the pancreas into the duodenum. This enzyme continues the breakdown of starch into maltose and other oligosaccharides. The optimal pH for amylase activity is around neutral (pH 7), which is achieved in the small intestine .

(b) Maltase Breaks Down Maltose to Glucose

• Action on the Brush Border: After starch has been broken down into maltose, this disaccharide is further digested by maltase, an enzyme located on the brush border (microvilli) of the epithelial cells lining the small intestine. Maltase hydrolyzes maltose into two glucose molecules through the cleavage of the glycosidic bond .
• Absorption of Glucose: The resulting glucose molecules are then absorbed through the intestinal epithelium into the bloodstream. This absorption primarily occurs in the jejunum, where glucose can be transported into enterocytes via specific transport mechanisms