Question

On hydrolysis, which of the following carbohydrates gives only glucose ?

• A. Starch
• B. Sucrose
• C. Lactose
• D. Galactose

Hint:

Starch, glycogen and cellulose are polymers of glucose. Hydrolysis of these carbohydrates ultimately produces only glucose molecules.

Answer 1

The Correct Option is A

Step 1: Eliminate galactose.
Galactose is a monosaccharide and cannot be hydrolyzed further. It does not yield glucose on hydrolysis.
Step 2: Eliminate sucrose and lactose.
Sucrose hydrolyzes to glucose + fructose. Lactose hydrolyzes to glucose + galactose. Both give two different monosaccharides, so neither yields only glucose.
Step 3: Starch gives only glucose.
Starch is a polysaccharide composed entirely of glucose units linked by $\alpha$-1,4 and $\alpha$-1,6 glycosidic bonds. Complete hydrolysis yields only glucose.
\[ \boxed{\text{Starch}} \]