Test for the presence of a reducing sugar (aka glucose) (LC 2026) (Leaving Cert Biology): Revision Notes

Test for the presence of a reducing sugar (glucose)

Background:

Glucose is a reducing sugar, which is a monosaccharide and a source of energy. A monosaccharide is a single sugar subunit and a type of carbohydrate. The general formula for carbohydrates is Cₓ(H₂O)ᵧ. The chemical formula for glucose is C₆H₁₂O₆.

Materials needed:

• Food sample
• Distilled water (control)
• Benedict's solution
• Test tubes
• Water bath
• Thermometer
• Timer

Method:

1. Add food sample to a test tube. Place distilled water in another test tube (control).
2. Add Benedict's solution.
3. Heat solution in a boiling water bath for 3-5 minutes.
4. Record colour change.
5. Repeat for control sample which is distilled water.

Result:

A positive result for the presence of a reducing sugar is blue to brick red/orange.

Control remains blue.