BIological Molecules - Reducing And Non-Reducing Sugar Flashcards
(12 cards)
What is reduction?
The gain of electrons or hydrogen
What is a reducing sugar?
A sugar that can donate electrons to another chemical
what is Benedict’s reagent?
An alkaline solution of copper (II) sulfate
When a reducing sugar is heated with Benedict’s reagent what is formed?
An insoluble red precipitate of copper (1) oxide
How is the Benedict’s test carried out?
Add 2cm^3 of food sample in a test tube
Add 2cm^3 of Benedict’s reagent
Heat in water bath for five minutes
What is the positive result for a reducing sugar when Benedict’s test is carried out?
The solution turns from blue to blue black
Give examples of reducing sugars
Monosaccharides and some disaccharides
Give examples of non reducing sugars
Sucrose
In order to detect a non reducing sugar, what must be done to the reducing sugar?
It must be hydrolysed into its monosaccharide components by hydrolysis
Describe the process of testing for non reducing sugars?
- add 2cm^3 of food sample With 2cm^3 of Benedict’s reagent
- place in a water bath for five mins and if no colour change then a reducing sugar is not present
- add 2cm^3 of food sample to 2cm^3 of dilute hydrochloric acid in a test tube and place in water bath
- slowly add sodium hydrogen carbonate solution to the test tube in order to neutralise the acid - use pH paper to check if alkaline
- again carry out the Benedict’s test and if non reducing sugar is present the solution will turn orange brown
Why is dilute hydrochloric acid used in the test for non-reducing sugars?
In order to hydrolyse the non reducing sugar into it’s monosaccharide components
What is the purpose of sodium hydrogen carbonate in the non reducing sugar test?
In order to neutralise the hydrochloric acid as Benedict’s reagent does not work in acidic conditions
