Question

Which of the following is a reducing sugar?

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

Answer 1

Answer: (A)

Galactose

Sugar is a substance which is crystalline, sweet in taste and soluble in water. A compound which acts as a reducing agent because of the presence of either ketoses or aldoses group forms a reducing sugar. All monosaccharides (cannot be hydrolyzed further) come under reducing sugar. Disaccharides which have aldehydic and ketonic group free, act as reducing sugars eg: maltose and lactose.

Galactose( $C_6{H}_{12}{O}_6$) is a monosaccharide. It is as sweet as glucose. As shown in the above fig, the structure of galactose is same as that of glucose, but it differs in the arrangements of atoms. Since it is a monosaccharide, it is a reducing sugar.