2. Disaccharides

Like monosaccharides, disaccharides are sugars but are formed by two monosaccharides joining together.

The most common disaccharides are maltose (glucose + glucose), sucrose (glucose + fructose) and lactose (glucose + galactose).

Sucrose is the transport sugar in plants, and the sugar commonly bought in stores. Lactose is the sugar bought in shops.


The joining of two monosaccharides takes place by a process known as condensation (yields H2O). During the reaction two hydroxyl groups line up alongside each other. One combines with a Hydrogen atom from the other, to form water. This allows a oxygen ‘bridge’, which is called a glycosidic bond.

The reverse of condensation is the addition of water, or hydrolysis.


1.1.3 Polysaccharides

1.1.4 Practicals


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