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A Level Biology Lesson 5: 

The Benedict's Test for Reducing and

Non-Reducing sugars

Task 1. Check Where this Lesson fits into your Exam Specification!

Task 2. Watch the Revision Notes Lesson in Full.

00:00 Learning Outcomes

00:24 What is a Reducing Sugar?

01:16 Non-Reducing Sugars

01:41 To test a Sample... we use the Benedict's Test.

02:05 How Benedict's Reagent Works.

02:20 Describe how to Carry out the Benedict's Test for Reducing Sugars

02:45 Expected Results

03:16 Describe how to Carry out the Benedict's Test for Non-Reducing Sugars

04:11 In Summary

Task 3. 

Download, Print out & complete the accompanying Interactive Worksheet.

05.-The-Benedict's-test-for-sugars.png
The-Benedict's-test-for-sugars--A3-Revis

A-Level Biology "The Benedict's Test for Reducing and Non-Reducing Sugars" Lesson 5. Summary.

Sugars can be classified as either Reducing or Non-Reducing. Monosaccharides and some disaccharides are reducing sugars – A sugar with a “free” Aldehyde [CO] or Ketone group [CHO]. These functional groups allow the sugar to donate electrons – making that sugar the “reductant” i.e. the “Reducing Sugar”. Thus, it is the reduction of Copper II Sulphate that gives the colour change when testing for the presence of reducing sugars in a test sample.

 

The reducing sugars you must know are: - 

  • Glucose

  • Fructose

  • Lactose

 

The only non-reducing sugar you must know is Sucrose.

 

You could be asked to Describe, Explain, Analyse and Evaluate the procedure testing for Reducing and / or Non-Reducing Sugars.

 

The Benedict’s test for reducing sugars: -

 

  1. Heat the test sample with Benedict’s Reagent.

  2. Observe the colour change.

  3. A brick red precipitate indicates the presence of a reducing sugar.

 

The Benedict’s test for non-reducing sugars: -

 

  1. Heat the test sample with dilute hydrochloric acid.

  2. Neutralise the test sample by adding sodium hydrocarbonate.

  3. Heat the test sample with Benedict’s Reagent.

  4. Observe the colour change.

  5. A brick red precipitate indicates the presence of a reducing sugar.

 

Check Your Spec!

★ AQA Specification Reference: - 3.1 Biological molecules: 3.1.2 Carbohydrates. Students could use, and interpret the results of qualitative tests - The Benedict's Test for reducing and non-reducing sugars.

 

★ CIE Specification Reference: - 2 Biological Molecules: Testing for biological molecules. a) carry out tests… The Benedict's Test for reducing and non-reducing sugars.

 

★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Appendix 5c: Use of apparatus and Techniques. 6. use qualitative reagents to identify biological molecules

 

★ Edexcel (Biology B) Specification Reference: - Appendix 5c: Use of apparatus and Techniques. 6. use qualitative reagents to identify biological molecules

 

★ OCR (Biology A) Specification Reference: - 2.1.2 Biological molecules (q) how to carry out and interpret the results of The Benedict's Test for reducing and non-reducing sugars.

 

★ OCR (Biology B) Specification Reference: - Module 2: Cells, chemicals for life, transport and gas exchange. Use of qualitative reagents to identify biological molecules. The Benedict's Test for reducing and non-reducing sugars.

 

★ WJEC Specification Reference: - Core Concepts 1. Chemical elements are joined together to form biological compounds - SPECIFIED PRACTICAL WORK - Food tests to include: The Benedict's Test for reducing and non-reducing sugars.