Monosaccharides (AQA A Level Biology)

Monosaccharides: Common Examples

• Sugars can be classified as reducing or non-reducing; this classification is dependent on their ability to donate electrons

• Reducing sugars can donate electrons (the carbonyl group becomes oxidised), the sugars become the reducing agent

  • Thus reducing sugars can be detected using Benedict’s test as they reduce the soluble copper sulphate to insoluble brick-red copper oxide

•  Examples of reducing sugars include: glucose, fructose and galactose

  • Fructose and galactose have the same molecular formula as glucose however they have a different structural formula

  • The different arrangement of atoms in these monosaccharides gives them slightly different properties

• Non-reducing sugars cannot donate electrons, therefore they cannot be oxidised

  • To be detected non-reducing sugars must first be hydrolysed to break the disaccharide into its two monosaccharides before a Benedict’s test can be carried out

  • Example: sucrose

The is a helpful mnemonic to remember the definitions of oxidation and reduction.