Carbohydrates & Metabolism Overview

Carbohydrates

• Indigestible polysaccharides are components of dietary fiber that pass through the intestines to feces
• Cellulose, a type of indigestible polysaccharide, cannot be cleaved by human enzymes due to its β-1,4 bonds

Metabolism

• Metabolism refers to the processing of dietary components after digestion and absorption
• Anabolic pathways are synthetic processes focused on synthesizing compounds
• Anabolic reactions combine smaller molecules such as amino acids to form larger molecules like proteins
• These reactions are endergonic, meaning they store energy, primarily derived from ATP breakdown
• The electron donor NADPH often provides the reducing power in anabolic reactions

Absorption of Glucose, Fructose, and Galactose

• Glucose, fructose, and galactose are the final products of carbohydrate digestion, absorbed by intestinal epithelial cells
• Galactose and glucose utilize the sodium-dependent glucose cotransporter 1 (SGLT-1) for active transport into mucosal cells
• Fructose is absorbed through a sodium-independent transporter called GLUT-5

Glycosidases

• Glycosidases are enzymes that act on glycosyl residues, breaking specific bonds based on structure and configuration
• The end products of carbohydrate digestion are monosaccharides: glucose, galactose, and fructose, absorbed by small intestine cells

This quiz covers the basics of carbohydrates, focusing on indigestible polysaccharides like cellulose and their role in dietary fiber. Additionally, it explores metabolism, particularly anabolic pathways involved in synthesizing compounds from dietary components.