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Author: Admin | 2025-04-28
Amino acids, lipids into fatty acids and glycerol, and nucleic acids into nitrogen bases and sugars. Some chemical digestion takes place in the mouth and stomach, but most of it occurs in the first part of the small intestine (duodenum).Digestive EnzymesChemical digestion could not occur without the help of many different digestive enzymes. Enzymes are proteins that catalyze or speed up biochemical reactions. Digestive enzymes are secreted by exocrine glands or by the mucosal layer of the epithelium lining the gastrointestinal tract. In the mouth, digestive enzymes are secreted by salivary glands. The lining of the stomach secretes enzymes, as does the lining of the small intestine. Many more digestive enzymes are secreted by exocrine cells in the pancreas and carried by ducts to the small intestine. Table \(\PageIndex{1}\) lists several important digestive enzymes, the organs and/or glands that secrete them, and the compounds they digest. You can read more about them in the text. Table \(\PageIndex{1}\): Digestive Enzymes Digestive Enzyme Organ, Glands That Secretes It Compound It Digests Amylase Salivary Glands, Pancreas Amylose (Polysaccharide) Sucrase Small Intestine Sucrose (Disaccharide) Lactase Small Intestine Lactose (Disaccharide) Lipase Salivary Glands, Pancreas Lipid Pepsin Stomach Protein Trypsin Pancreas Protein Chymotrypsin Pancreas Protein Deoxyribonuclease Pancreas DNA Ribonuclease Pancreas RNA Nuclease Small Intestine Small Nucleic Acids Chemical Digestion of CarbohydratesAbout 80 percent of digestible carbohydrates in a typical Western diet are in the form of the plant polysaccharide amylose, which consists mainly of long chains of glucose and is one of two major components of starch. Additional dietary carbohydrates include the animal polysaccharide glycogen, along with some sugars, which are mainly disaccharides.To chemically digest amylose and glycogen, the enzyme amylase is required. The chemical digestion of these polysaccharides begins in the mouth, aided by amylase in saliva. Saliva also contains mucus, which lubricates the food,
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