ASBiologyCambridge (CIE)Revision Notes2. Biological MoleculesCarbohydrates & LipidsReducing & Non-Reducing Sugars

Reducing & Non-Reducing Sugars (Cambridge (CIE) AS Biology): Revision Note

Exam code: 9700

Cara Head

Written by: Cara Head

Reviewed by: Alistair Marjot

Updated on

Reducing & non-reducing sugars

  • 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 the Benedict’s test as they reduce the soluble copper sulphate to insoluble brick-red copper oxide

    • Examples: glucose, fructose, maltose

  • 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

Diagram explaining OIL RIG; oxidation is the loss of electrons, reduction is the gain of electrons, with highlighted words for clarity.
The mnemonic to remember the definitions for oxidation and reduction

Examiner Tips and Tricks

Become familiar with the OILRIG mnemonic to remember what happens to a molecule when electrons are lost from it (oxidation) or gained by it (reduction). 

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    Author
    Reviewer
    Cara Head

    Author: Cara Head

    Expertise: Biology & Psychology Content Creator

    Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding

    Alistair Marjot

    Reviewer: Alistair Marjot

    Expertise: Environmental Systems and Societies & Biology Content Creator

    Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.