Enzymes and Transporters for Carbohydrates Digestion Quiz

Dietary Carbohydrates and Digestion

• Principal dietary carbohydrate of humans is starch.
• Salivary α-amylase is the enzyme responsible for the digestion of starch and glycogen in the mouth.
• Major hydrolysis products of salivary α-amylase on starch and glycogen include maltose and maltotriose.
• Action of salivary α-amylase in the stomach diminishes after about 20 minutes due to acidic pH conditions.
• Pancreas produces pancreatic α-amylase for carbohydrate digestion in the small intestine.
• Optimum pH for pancreatic α-amylase activity ranges from 6.7 to 7.0.

Enzymatic Hydrolysis and Transport

• Sucrose is NOT a principal dietary carbohydrate of humans, as it is a disaccharide.
• Enzyme that hydrolyzes α-(1→4)-glycosidic linkages between monosugar residues is glucoamylase.
• Major hydrolysis product of pancreatic α-amylase is maltose.
• Enzyme responsible for hydrolyzing α-(1→4)- and α-(1→6)-glucosidic linkages is isomaltase.
• Enzymes involved in hydrolysis of dietary disaccharides such as sucrose and lactose include sucrase and lactase.
• Glucose, galactose, and fructose are transported into absorptive epithelial cells of the small intestine primarily via sodium-glucose transport proteins (SGLT).
• GLUT protein families found in each cell demonstrate the role of glucose metabolism, with GLUT1, GLUT2, and GLUT4 being the most common.

Metabolism and Fate of Carbohydrates

• Most dietary galactose is converted to glucose after absorption into liver cells.
• Peripheral glucose after uptake and transport is utilized for energy production or stored as glycogen.
• Main hydrolysis product of intestinal enzymes is monosaccharides.
• After transport into liver cells, fructose and glucose undergo further metabolism, with fructose being converted into intermediates for energy production or lipid synthesis.