Lactose is a disaccharide of

Options

A. glucose only
B. glucose and fructose
C. glucose and galactose
D. all of the above

Answer

To answer the question "Lactose is a disaccharide of what?", we can follow these steps:

### Step-by-Step Solution:

1. **Definition of Lactose**: Start by understanding what lactose is. Lactose is a type of sugar known as a disaccharide.

2. **Composition of Lactose**: Identify the components that make up lactose. It is composed of two monosaccharides.

3. **Identify the Monosaccharides**: The two monosaccharides that combine to form lactose are D-galactose and D-glucose.

4. **Bond Formation**: Understand how these two monosaccharides are linked together. They are joined by a specific type of bond known as a beta 1,4-galactosidic bond.

5. **Conclusion**: Therefore, lactose is a disaccharide made up of one molecule of D-galactose and one molecule of D-glucose.

### Final Answer:
Lactose is a disaccharide composed of D-galactose and D-glucose.

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