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Disaccharide

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Definition

noun, plural: disaccharides

A (carbohydrate) composed of two monosaccharides, thus yields two monosaccharide molecules on complete hydrolysis


Supplement

Carbohydrates are organic compounds comprised of carbon, hydrogen, and oxygen, usually in the ratio of 1:2:1. They are one of the major classes of biomolecules. They are an important source of energy. They also serve as structural components. They are classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

A disaccharide is a carbohydrate that forms when two monosaccharides are joined by a glycosidic linkage. The monosaccharides combine to form a disaccharide through condensation reaction, a process where a water molecule is removed from the functional group. The most common types of disaccharides are sucrose, lactose, and maltose. Sucrose (common table sugar) is a disaccharide formed by the combination of glucose and fructose. Lactose (milk sugar) is formed by the combination of glucose and galactose. Maltose (malt sugar) is produced when two glucose units are joined together. These three disaccharides are isomers with a general chemical formula of C12H22O11.

A disaccharide may be reverted to its monomeric monosaccharide components through hydrolysis with the help of the enzyme disaccharidases (e.g. sucrase, lactase, and maltase for the degradation of sucrose, lactose, and maltose, respectively). While condensation reaction involves the elimination of water, hydrolysis utilizes a water molecule.

Disaccharides may be classified into reducing and non-reducing. Examples of a reducing disaccharide are maltose and cellubiose. Non-reducing disaccharides are sucrose and trehalose.

Other examples of disaccharides are lactulose, chitobiose, kojibiose, nigerose, isomaltose, sophorose, laminaribiose, gentiobiose, turanose, maltulose, trehalose, palatinose, gentiobiulose, mannobiose, melbiose, melibiulose, rutinose, rutinulose, and xylobiose.


Word origin: di- ("two") + saccharide

Also called:

  • double sugar

Synonym(s):

  • biose

See also: