sugulussidemed

Sugulussidemed (glycosidic bonds) are covalent linkages that join carbohydrate units or attach a sugar to another molecule. They are formed by a dehydration synthesis between the anomeric carbon of a sugar and a hydroxyl group on another sugar or a non-sugar acceptor, releasing a molecule of water. Most sugar–sugar linkages in polysaccharides are O-glycosidic bonds, and the stereochemistry at the anomeric carbon is described as alpha or beta.

In carbohydrates, common linkages include alpha-1,4 and alpha-1,6, as seen in starch (amylose and amylopectin), which determine helical structure and digestion. Cellulose features beta-1,4 linkages, giving rigid, fibrous fibers that are not digestible by humans. Disaccharides illustrate diversity: maltose has an alpha-1,4 bond between glucose units; lactose has a beta-1,4 bond between galactose and glucose; sucrose contains a unique alpha-1,2 linkage between glucose and fructose and is non-reducing because both anomeric carbons are involved.

Glycosidic bonds also occur in glycosylation, where sugars attach to proteins or lipids, forming N- or O-glycosidic bonds in biomolecules. C-glycosidic bonds, where carbon–carbon linkages form between sugar rings and aglycones, are found in some natural products.

Biologically, glycosidic bonds determine the digestibility, solubility, and structural properties of carbohydrates. They are cleaved by specific enzymes, such as amylases, maltases, lactases, and sucrases, or by acid hydrolysis, enabling energy retrieval and metabolism. The diversity and stability of glycosidic bonds underpin polysaccharide function, food chemistry, and many cellular processes.