Which of the following disaccharide gives a ketose and an aldose only on hydrolysis ?

Options

A. Sucrose
B. Maltose
C. Lactose
D. All the three

Answer

To determine which disaccharide gives a ketose and an aldose upon hydrolysis, we need to analyze the hydrolysis products of the given disaccharides: sucrose, maltose, and lactose.

### Step-by-Step Solution:

1. **Identify the Disaccharides**: The disaccharides in question are sucrose, maltose, and lactose.

2. **Understand Hydrolysis**: Hydrolysis of a disaccharide involves breaking the glycosidic bond between the two monosaccharide units using water.

3. **Analyze Sucrose**:
- Sucrose is composed of glucose (an aldose) and fructose (a ketose).
- Upon hydrolysis, sucrose yields:
- **Alpha-D-glucose** (an aldose)
- **Beta-D-fructose** (a ketose)

4. **Analyze Maltose**:
- Maltose is composed of two glucose units (both aldoses).
- Upon hydrolysis, maltose yields:
- **Two alpha-D-glucose molecules** (both aldoses)

5. **Analyze Lactose**:
- Lactose is composed of glucose (an aldose) and galactose (also an aldose).
- Upon hydrolysis, lactose yields:
- **Glucose** (an aldose)
- **Galactose** (an aldose)

6. **Conclusion**:
- Only sucrose gives one aldose (alpha-D-glucose) and one ketose (beta-D-fructose) upon hydrolysis.
- Therefore, the disaccharide that gives a ketose and an aldose only on hydrolysis is **sucrose**.

### Final Answer:
The disaccharide that gives a ketose and an aldose only on hydrolysis is **sucrose**.