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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: OCR Biology A (H020), AS-level, 2.1.2 Biological molecules. Topic: Biological Molecules.

Key terms in this lesson

condensation reaction
A reaction that joins two molecules together with a covalent bond, releasing a water molecule.
hydrolysis
A reaction that breaks a covalent bond between two molecules by adding a water molecule.

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