Chapter 25 - Section 25.6 - Study Guide - Assess Your Learning Outcomes - Page 992: 1

Carbohydrate digestion is a complex process that involves the breakdown of complex carbohydrates (starches and disaccharides) into simpler sugars (monosaccharides) for absorption in the digestive tract. Here are the steps involved in carbohydrate digestion from the mouth to the small intestine, along with the enzymes responsible and their contributions: 1. Mouth (Oral Cavity): - Enzyme: Salivary Amylase - Contribution: Salivary amylase, secreted by salivary glands, begins the digestion of starch into smaller polysaccharides (oligosaccharides) and maltose (a disaccharide consisting of two glucose molecules) in the mouth. The process starts breaking down the long chains of starch into shorter segments. 2. Stomach: - No significant carbohydrate digestion occurs in the stomach due to the acidic environment, which denatures salivary amylase and inhibits its activity. 3. Small Intestine (Duodenum and Jejunum): - Enzyme: Pancreatic Amylase - Contribution: Pancreatic amylase, released by the pancreas into the duodenum, continues the breakdown of polysaccharides into smaller oligosaccharides and maltose. The pancreas plays a crucial role in providing enzymes for efficient carbohydrate digestion. 4. Small Intestine (Jejunum and Ileum): - Enzymes: Maltase, Isomaltase, Sucrase, Lactase - Contribution: These enzymes are present on the brush border of the small intestine lining. They further break down the oligosaccharides and disaccharides into monosaccharides: - Maltase: Breaks down maltose into two glucose molecules. - Isomaltase: Breaks down isomaltose into two glucose molecules. - Sucrase: Breaks down sucrose (a disaccharide consisting of glucose and fructose) into glucose and fructose. - Lactase: Breaks down lactose (a disaccharide consisting of glucose and galactose) into glucose and galactose. 5. Absorption: - The monosaccharides (glucose, fructose, and galactose) resulting from carbohydrate digestion are absorbed through the intestinal wall and into the bloodstream. - Glucose and galactose are absorbed via active transport, while fructose is absorbed via facilitated diffusion. 6. Transport to the Liver: - The absorbed monosaccharides are transported to the liver via the hepatic portal vein. In the liver, some fructose and galactose may be converted to glucose for storage or immediate energy use. The collective action of these enzymes, starting from the mouth and progressing through the small intestine, ensures the effective digestion of complex carbohydrates into absorbable monosaccharides, which can then be utilized for energy or stored as glycogen in the liver and muscles.

Carbohydrate digestion is a complex process that involves the breakdown of complex carbohydrates (starches and disaccharides) into simpler sugars (monosaccharides) for absorption in the digestive tract. Here are the steps involved in carbohydrate digestion from the mouth to the small intestine, along with the enzymes responsible and their contributions: 1. Mouth (Oral Cavity): - Enzyme: Salivary Amylase - Contribution: Salivary amylase, secreted by salivary glands, begins the digestion of starch into smaller polysaccharides (oligosaccharides) and maltose (a disaccharide consisting of two glucose molecules) in the mouth. The process starts breaking down the long chains of starch into shorter segments. 2. Stomach: - No significant carbohydrate digestion occurs in the stomach due to the acidic environment, which denatures salivary amylase and inhibits its activity. 3. Small Intestine (Duodenum and Jejunum): - Enzyme: Pancreatic Amylase - Contribution: Pancreatic amylase, released by the pancreas into the duodenum, continues the breakdown of polysaccharides into smaller oligosaccharides and maltose. The pancreas plays a crucial role in providing enzymes for efficient carbohydrate digestion. 4. Small Intestine (Jejunum and Ileum): - Enzymes: Maltase, Isomaltase, Sucrase, Lactase - Contribution: These enzymes are present on the brush border of the small intestine lining. They further break down the oligosaccharides and disaccharides into monosaccharides: - Maltase: Breaks down maltose into two glucose molecules. - Isomaltase: Breaks down isomaltose into two glucose molecules. - Sucrase: Breaks down sucrose (a disaccharide consisting of glucose and fructose) into glucose and fructose. - Lactase: Breaks down lactose (a disaccharide consisting of glucose and galactose) into glucose and galactose. 5. Absorption: - The monosaccharides (glucose, fructose, and galactose) resulting from carbohydrate digestion are absorbed through the intestinal wall and into the bloodstream. - Glucose and galactose are absorbed via active transport, while fructose is absorbed via facilitated diffusion. 6. Transport to the Liver: - The absorbed monosaccharides are transported to the liver via the hepatic portal vein. In the liver, some fructose and galactose may be converted to glucose for storage or immediate energy use. The collective action of these enzymes, starting from the mouth and progressing through the small intestine, ensures the effective digestion of complex carbohydrates into absorbable monosaccharides, which can then be utilized for energy or stored as glycogen in the liver and muscles.