Question

state the difference in the structures of the nutritionally important disaccharides

Answer 1

Disaccharides are carbohydrates composed of two monosaccharide units linked together by a glycosidic bond. Here are the three nutritionally important disaccharides and their structural differences:

1. **Sucrose**:
- **Composition**: Composed of glucose and fructose.
- **Linkage**: The glycosidic bond is an α(1→2) linkage between the anomeric carbon of glucose (C1) and the anomeric carbon of fructose (C2).
- **Structure Representation**: It has a non-reducing sugar nature because both anomeric carbons are involved in the bond.

2. **Lactose**:
- **Composition**: Composed of glucose and galactose.
- **Linkage**: The glycosidic bond is a β(1→4) linkage between the anomeric carbon of galactose (C1) and carbon 4 of glucose.
- **Structure Representation**: It has a reducing sugar nature because the anomeric carbon of glucose is free and can open up to its aldehyde form.

3. **Maltose**:
- **Composition**: Composed of two glucose molecules.
- **Linkage**: The glycosidic bond is an α(1→4) linkage between the anomeric carbon of the first glucose (C1) and carbon 4 of the second glucose.
- **Structure Representation**: It has a reducing sugar nature because the anomeric carbon of one glucose unit is free.

### Summary of Differences:
- **Monosaccharide Units**: Sucrose (glucose + fructose), Lactose (glucose + galactose), Maltose (glucose + glucose).
- **Type of Glycosidic Bond**:
- Sucrose: α(1→2)
- Lactose: β(1→4)
- Maltose: α(1→4)
- **Reducing vs. Non-Reducing**:
- Sucrose is non-reducing.
- Lactose and Maltose are reducing sugars.

These structural characteristics significantly influence the digestion and nutritional properties of each disaccharide.