Question

Two statements are given below: 

I. Milk sugar is a disaccharide of \( \alpha \)-D-galactose and \( \beta \)-D-glucose. 
II. Sucrose is a disaccharide of \( \alpha \)-D-glucose and \( \beta \)-D-fructose. The correct answer is:

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

Hint:

Lactose (milk sugar) is composed of \( \beta \)-D-galactose and \( \beta \)-D-glucose, whereas sucrose (table sugar) consists of \( \alpha \)-D-glucose and \( \beta \)-D-fructose.

Answer 1

The Correct Option is D

Step 1: Understanding the Structure of Disaccharides 
1. Milk Sugar (Lactose)
- Lactose is composed of \( \beta \)-D-galactose and \( \beta \)-D-glucose, not \( \alpha \)-D-galactose.
- The glycosidic bond in lactose is a \( \beta \)-1,4 linkage.
2. Sucrose (Table Sugar)
- Sucrose is composed of \( \alpha \)-D-glucose and \( \beta \)-D-fructose.
- It has a \( \alpha \)-1,2 glycosidic linkage.
Step 2: Evaluating the Statements 
- Statement I is incorrect, as lactose contains \( \beta \)-D-galactose, not \( \alpha \)-D-galactose.
- Statement II is correct, as sucrose consists of \( \alpha \)-D-glucose and \( \beta \)-D-fructose.
Step 3: Evaluating the Given Options 
- Option (1): Incorrect, as statement I is incorrect.
- Option (2): Incorrect, as statement II is correct.
- Option (3): Incorrect, as statement I is incorrect.
- Option (4): Correct, as statement I is incorrect and statement II is correct.
Thus, the correct answer is Option (4).