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 and complete the accompanying Benedict's test work booklet and revision notes.

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

Lesson Summary: A Level Biology

The Benedict's Test for Reducing and Non-Reducing sugars

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

 

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

 

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

 

OCR A Level Biology (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 A Level Biology (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 A Level Biology 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.

★ BTEC Level 3 Nationals in Applied Science. Unit 10: Biological Molecules and Metabolic Pathways: A: Understand the structure and function of biological molecules and their importance in maintaining biochemical processes.  A2 Carbohydrates: Structure and features: contain carbon (C), hydrogen and oxygen atoms. Monosaccharides, e.g. α and β glucose, galactose, fructose, ribose and deoxyribose. Disaccharides, e.g. lactose, maltose and sucrose. Polysaccharides, e.g. amylose, amylopectin, cellulose. Use of iodine and Benedicts’ solution as tests for presence of carbohydrates.

 

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