Glycosidic linkages are hydrolyzed, or broken, through the addition of a water molecule and a catalyst.
Carbohydrates bond with each other through glycosidic linkages. These bonds form via a dehydration reaction, also known as a condensation reaction or dehydration synthesis. In this process, the hydroxyl group of one monosaccharide combines with the hydrogen of another, releasing a molecule of water and forming a covalent bond. For instance, the diagram below shows glucose and fructose monomers combining via a dehydration reaction to form sucrose, a disaccharide we know as table sugar. Note that a water molecule is released in this reaction, but isn’t shown.
Likewise, glycosidic linkages are broken through the addition of a water molecule in a hydrolysis reaction. Hydrolysis assists the release of monosaccharides for metabolism. Different linkages require specific enzymes for hydrolysis to break the bond. For instance, the enzyme amylase, found in our saliva, initiates the digestive process by catalyzing the breakdown of starch into glucose molecules. Glycosidase enzymes also catalyze the cleavage of glycosidic bonds in carbohydrates.
Practice Questions
Khan Academy
Hemiacetal formation of carbohydrates
MCAT Official Prep (AAMC)
Key Points
• The hydrolysis of glycosidic linkages occurs through the addition of a water molecule and the action of a catalyst.
• Different linkages require specific enzymes for hydrolysis to break the bond, allowing monosaccharides to be released for metabolism.
• Glycosidase enzymes catalyze the cleavage of glycosidic bonds in carbohydrates.
Key Terms
Glycosidic bonds (linkages): A type of covalent bond that joins two carbohydrate molecules.
Hydrolysis: The breakage of a glycosidic linkage by the addition of a water molecule and the action of a catalyst.
Catalyst: A substance (in this case, an enzyme) that speeds up a chemical reaction.
Dehydration reaction: A reaction that forms a covalent bond between two monosaccharides through the release of a molecule of water.
Glycosidase: A family of enzymes that catalyze the cleavage of glycosidic linkages in carbohydrates through hydrolysis reactions.