Question

Given below are two statements :
Statement I : Maltose is a non-reducing sugar
Statement II : Lactose is a reducing sugar

• A. Both statement I and statement II are correct
• B. Statement I is correct but statement II is incorrect
• C. Statement I is incorrect but statement II is correct
• D. Both statement I and statement II are incorrect

Hint:

Among common disaccharides, \textbf{Sucrose} is the only non-reducing sugar because both anomeric carbons (C1 of glucose and C2 of fructose) are involved in the glycosidic bond.
Maltose and Lactose are always reducing.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question evaluates whether common disaccharides (maltose and lactose) are reducing or non-reducing sugars based on their structural features.
Step 3: Detailed Explanation:
A sugar is reducing if it has a free anomeric carbon (hemiacetal or hemiketal group) that can open into an aldehyde or ketone form to reduce Tollens' or Fehling's reagents.
Analysis of Statement I:
Maltose consists of two glucose units linked by an $\alpha(1 \to 4)$ glycosidic bond.
While the C1 of the first glucose is involved in the bond, the C1 of the second glucose is free (hemiacetal).
Thus, Maltose is a reducing sugar. Statement I is incorrect.
Analysis of Statement II:
Lactose consists of galactose and glucose linked by a $\beta(1 \to 4)$ glycosidic bond.
The C1 of glucose remains free as a hemiacetal group.
Thus, Lactose is a reducing sugar. Statement II is correct.
Step 4: Final Answer:
Statement I is incorrect, and Statement II is correct.