In this A-Level Biology Lesson "The Benedict's Test for Reducing and Non-Reducing sugars” you'll learn what makes a Reducing sugar a Reducing sugar.

Next Non-Reducing sugars will be discussed before moving on to the Benedict's Test and How Benedict's Reagent works.

Remember!

You'll have to be able to "Describe how to carry out the Benedict's test for Reducing sugars and explain the expected results - so that's covered before moving on to describe how to carry out the Benedict's Test for Non-Reducing Sugars.

When you’re confident you know how to describe the Benedict's test procedure for both Reducing and Non-Reducing sugars and explain the expected results it's time for you to complete the accompanying “Benedict's Test for Reducing and Non-Reducing sugars” knowledge check and exam style questions in your lesson workbooklet. 

Don't worry, you’ll be able to check your answers with my properly written answers in the back of the workbook. (No vague mark schemes here either, you’ll see exactly how you need write your answers so that you gain maximum marks in the exams!)

A Level Biology: - The Benedict's Test for Reducing and Non-Reducing sugars

​Here's a summary of the lesson: -

​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: -

Heat the test sample with Benedict’s Reagent.

Observe the colour change.

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

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

Heat the test sample with dilute hydrochloric acid.

Neutralise the test sample by adding sodium hydrocarbonate.

Heat the test sample with Benedict’s Reagent.

Observe the colour change.

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