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Disaccharides

Two monosaccharides joined together by a covalent bonds is called a disaccharide.The monosaccharides undergo a condensation reaction with the removal of a water molecule to form the covalent bond.The bond formed is called a glycosidic bond.Two α-glucose molecules join together by an α-1,4-glycosidic bond to form maltose.
An α-glucose molecule and a galactose molecule joined together by a glycosidic bond to form lactose.An α-glucose molecule and a fructose molecule joined together by a glycosidic bond to form sucrose.Two α-glucose molecules joined together by a glycosidic bond form maltose.The monosaccharides may be regenerated by hydrolysis.

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Specification: AQA Biology (7401), AS-level, 3.1.2 Carbohydrates. Topic: Biological Molecules.

Key terms in this lesson

covalent bond
A strong chemical bond formed when a pair of electrons is shared between two atoms.
condensation reaction
A reaction that joins two molecules together with a covalent bond, with the elimination of a water molecule.
hydrolysis
The breaking of a covalent bond within a molecule using a water molecule.
monosaccharide
The monomer from which larger carbohydrates are made, a simple sugar such as glucose.

More in Biological Molecules

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