Disaccharides

A disaccharide forms when two monosaccharide units join together. Sucrose (common table sugar) is the classic example, formed from one molecule of alpha-glucose and one molecule of fructose. The two monosaccharides join through a condensation reaction, in which a molecule of water is released as the bond forms; the covalent bond that links the two sugar units is called a glycosidic bond. This reaction can run in reverse: a hydrolysis reaction adds a water molecule back in and splits the glycosidic bond, breaking the disaccharide back down into its two component monosaccharides - this is essentially what happens when a disaccharide like sucrose or lactose is digested in the gut. The condensation/hydrolysis pair - building a bond by removing water, breaking it by adding water back - i …