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GCSE Biology · key term
A sugar, such as glucose, that gives a positive result with heated Benedict’s solution.
Used by AQA, Edexcel and OCR
Specification 4.2.2.1 · Paper 1
A sugar, such as glucose, lactose or maltose, that gives a positive result with Benedict’s solution when heated.
Revise: Required Practicals: Food Tests and Amylase ActivityIf a reducing sugar is present, heating produces a change through green, yellow or orange to a brick-red precipitate, depending partly on how much reducing sugar is present. If none is detected, the solution remains blue.
Specification 1.13B · Paper 1, Paper 2
A sugar that reacts with heated Benedict’s solution; examples include glucose and lactose.
Revise: Food Tests InvestigationThese are qualitative tests: they are mainly used to decide whether starch, reducing sugar, protein or lipid is present. A food can give more than one positive result because it can contain several different nutrients.
Specification PAG 2 · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A sugar, such as glucose, that gives a positive result when heated with Benedict’s reagent.
Revise: Testing for biological moleculesTo test for a reducing sugar, such as glucose, put the sample in a test tube and add an equal volume or an excess of Benedict’s reagent. Place the tube in a hot water bath for a few minutes. Benedict’s reagent starts blue.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Example ActivityFood tests help you find out whether a sample contains starch, reducing sugars, protein or lipids. Each test uses a different reagent and produces an observable result. The result is qualitative: it indicates whether a molecule was detected, rather than giving its exact mass or concentration.
Do not say that Benedict’s solution tests for every sugar: it detects reducing sugars. Sucrose does not give a positive result unless it is first broken down.
Link each positive result to the molecule it identifies. Benedict’s test identifies reducing sugars, not every type of sugar.
Name the molecule detected, not just the food tested: Benedict’s solution tests for reducing sugars, not all sugars.
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