Question

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

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

Hint:

Maltose gives only glucose on hydrolysis. Sucrose gives glucose and fructose; lactose gives glucose and galactose.

Answer 1

The Correct Option is D

Step 1: Classify each carbohydrate as mono- or disaccharide.
Sucrose, lactose, and maltose are disaccharides. Galactose is a monosaccharide and does not hydrolyse further.
Step 2: Hydrolysis of sucrose.
\[ \text{Sucrose} \xrightarrow{H^+} \text{Glucose} + \text{Fructose} \] Sucrose gives glucose AND fructose, not only glucose.
Step 3: Galactose is a monosaccharide.
Galactose does not hydrolyse to give glucose. It is itself a monosaccharide.
Step 4: Hydrolysis of lactose.
\[ \text{Lactose} \xrightarrow{H^+} \text{Glucose} + \text{Galactose} \] Lactose gives glucose AND galactose, not only glucose.
Step 5: Hydrolysis of maltose.
\[ \text{Maltose} \xrightarrow{H^+} \text{Glucose} + \text{Glucose} \] Maltose consists of two glucose units joined by an alpha-1,4-glycosidic bond. Hydrolysis gives exclusively two molecules of glucose.
Step 6: State the final answer.
Only maltose gives exclusively glucose on hydrolysis. \[ \boxed{\text{Maltose}} \]