Lactose is made of

Options

A. `alpha-D`-galactose and `beta-D-`glucose
B. `alpha-D` glucose and `beta-D-` glucose
C. `beta-D-` galactose and `beta-D-` glucose
D. `beta-D-` galactose and `alpha-D-` glucose

Answer

To determine what lactose is made of, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Composition of Lactose**:
- Lactose is a disaccharide, which means it is composed of two monosaccharides.

2. **Identify the Monosaccharides**:
- The two monosaccharides that make up lactose are galactose and glucose.

3. **Determine the Forms of Monosaccharides**:
- Galactose is present in the form of beta-D-galactopyranose.
- Glucose is present in the form of beta-D-glucopyranose.

4. **Combine the Monosaccharides**:
- Therefore, lactose is formed by the combination of beta-D-galactose and beta-D-glucose.

5. **Final Answer**:
- The correct answer is that lactose is made of beta-D-galactose and beta-D-glucose.