Question

Which one of these is a reducing sugar ?

• A. Galactose
• B. Gluconic acid
• C. Sucrose
• D. $\beta$ -methylgalactoside.

Answer 1

The correct option is A Galactose

Reducing sugars are those sugars that possess an aldehyde group which can be easily oxidised to acid. Even those sugars that have a keto group which can tautomerize to aldehyde in solution possess the reducing property of sugars. Therefore glucose, fructose and galactose are reducing sugars.

Whereas gluconic acid, sucrose and $\beta$ -methyl galactoside do not contain a free aldehyde group, therefore do not have the reducing property of sugars.


1) Sucrose


2) Gluconic acid



3) $\beta$ -methylgalactoside