BRAINCAKETest for Sugars
Reducing sugars can donate electrons, reducing another chemical. All monosaccharides and most disaccharides (maltose, lactose) are reducing sugars. Sucrose is a non-reducing sugar.
Test for reducing sugars (Benedict's test).
1. Add an equal volume of Benedict's reagent (blue, containing copper(II) sulfate) to the sample in solution.
2. Heat in a boiling water bath for about 5 minutes.
3. A reducing sugar reduces blue Cu2+ ions to copper(I) oxide, which forms a brick-red precipitate.
If no reducing sugar is present, the solution stays blue. The colour depends on how much reducing sugar there is:
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Key terms in this lesson
- semi-quantitative
- Giving an approximate indication of how much of a substance is present, rather than an exact value.
- colorimeter
- An instrument that measures the amount of light of a particular colour absorbed by, or transmitted through, a solution.
More in Biological Molecules
- Organic Compounds
- Carbohydrates
- Monosaccharides
- Disaccharides
- Polysaccharides
- Starch
- Test for Starch
- Glycogen
All 25 lessons in Biological Molecules · All Edexcel AS-level Biology topics