Which statement is incorrect regarding Lactose?

Options

A. It is composed of `beta`-D(+)-Galactose & `beta`-D(+)-Glucose
B. It is a reducing sugar
C. It is a disaccharides `(C_12H_22O_11)` having eight -OH groups
D. It has glycosidic linkage of `C_1` of glucose & `C_4` OF galactose

Answer

To determine which statement is incorrect regarding lactose, we will analyze each option based on the structure and properties of lactose.

### Step-by-Step Solution:

1. **Understanding Lactose**:
- Lactose is a disaccharide composed of two monosaccharides: β-D-galactose and β-D-glucose.
- Its molecular formula is C₁₂H₂₂O₁₁.

2. **Structure of Lactose**:
- Lactose consists of a β-D-galactose unit linked to a β-D-glucose unit.
- The glycosidic linkage occurs between the first carbon (C1) of β-D-galactose and the fourth carbon (C4) of β-D-glucose.

3. **Analyzing the Statements**:
- **Statement 1**: Lactose is composed of β-D-galactose and β-D-glucose.
- This statement is correct.

- **Statement 2**: Lactose is a reducing sugar.
- Reducing sugars are those that can donate electrons or reduce another molecule. Lactose can be hydrolyzed to yield glucose and galactose, which have free aldehyde groups, making this statement correct.

- **Statement 3**: Lactose is a disaccharide with the formula C₁₂H₂₂O₁₁ and has 8 OH groups.
- This is also correct. The structure of lactose indeed contains 8 hydroxyl (OH) groups.

- **Statement 4**: Lactose has a glycosidic linkage of C1 of glucose and C4 of galactose.
- This statement is incorrect. The correct linkage is between C1 of β-D-galactose and C4 of β-D-glucose.

4. **Conclusion**:
- The incorrect statement regarding lactose is **Statement 4**.

### Summary of the Solution:
- The incorrect statement is that lactose has a glycosidic linkage of C1 of glucose and C4 of galactose; the correct linkage is C1 of galactose and C4 of glucose.