The disaccharide present in milk is

Options

A. Maltose
B. Ketose
C. Sucrose
D. Lactose

Explanation

**Step-by-Step Solution:**

1. **Identify the Disaccharide in Milk:**
- The disaccharide present in milk is known as lactose.

2. **Composition of Lactose:**
- Lactose is composed of two monosaccharides: glucose and galactose.

3. **Structure of Lactose:**
- The structure of lactose can be represented as a combination of one glucose molecule and one galactose molecule.
- Glucose and galactose are both six-carbon sugars (hexoses) and have similar structures but differ in the arrangement of hydroxyl groups.

4. **Formation of Glycosidic Linkage:**
- Lactose is formed through a glycosidic linkage, which occurs when a molecule of water is removed (a dehydration reaction) between the hydroxyl group of the glucose and the hydroxyl group of the galactose.
- This linkage is specifically a 1,4-glycosidic bond, indicating that the bond is formed between the first carbon of glucose and the fourth carbon of galactose.

5. **Conclusion:**
- Therefore, the disaccharide present in milk is lactose, which consists of one glucose unit and one galactose unit linked by a 1,4-glycosidic bond.

---