Disaccharides (AQA A Level Biology)

Disaccharides: Common Examples

• Monosaccharides can join together via condensation reactions to form disaccharides

  • A condensation reaction is one in which two molecules join together via the formation of a new chemical bond, with a molecule of water being released in the process

  • The new chemical bond that forms between two monosaccharides is known as a glycosidic bond

  • To calculate the chemical formula of a disaccharide, you add all the carbons, hydrogens and oxygens in both monomers then subtract 2x H and 1x O (for the water molecule lost)

• Common examples of disaccharides include:

  • Maltose (the sugar formed in the production and breakdown of starch)

  • Sucrose (the main sugar produced in plants)

  • Lactose (a sugar found only in milk)

• All three of the common examples above have the formula C₁₂H₂₂O₁₁

Common Disaccharides and their Monosaccharide Monomers Table

The disaccharide maltose is formed from two α-glucose monomers (sub-units)

The disaccharide sucrose is formed from α-glucose and fructose monomers (sub-units)