Which one of the following sets of monosaccharides forms sucrose ?

Options

A. `alpha`-D- galactopyranose and `alpha`-D-glucophyranose
B. `alpha`-D-glucopyranose and `beta`-D-fructofuranose
C. `alpha`-D-glucopyranose and `beta`-D-fructopyranose
D. `alpha`-glucopyranose and `beta`-D-fructopyranose

Explanation

To determine which set of monosaccharides forms sucrose, we need to identify the specific monosaccharides involved in its synthesis.

### Step-by-Step Solution:

1. **Identify the Structure of Sucrose**:
Sucrose is a disaccharide composed of two monosaccharides. It is formed from glucose and fructose.

2. **Identify the Specific Forms of Monosaccharides**:
- The glucose component in sucrose is in the **alpha-D-glucopyranose** form. This means it has a six-membered ring structure (pyranose) with the hydroxyl group (OH) on the first carbon atom positioned below the plane of the ring.
- The fructose component is in the **beta-D-fructofuranose** form. This means it has a five-membered ring structure (furanose) with the hydroxyl group on the second carbon atom positioned above the plane of the ring.

3. **Formation of Glycosidic Linkage**:
- To form sucrose, a glycosidic bond is created between the anomeric carbon of alpha-D-glucopyranose and the anomeric carbon of beta-D-fructofuranose.
- This occurs through a condensation reaction where a water molecule is removed (dehydration synthesis). Specifically, the hydroxyl group (OH) from fructose and a hydrogen atom (H) from glucose are removed to form water, allowing the two monosaccharides to bond.

4. **Conclusion**:
- The correct combination of monosaccharides that forms sucrose is **alpha-D-glucopyranose** and **beta-D-fructofuranose**.

5. **Select the Correct Option**:
- Among the given options, the only correct set that forms sucrose is **alpha-D-glucopyranose and beta-D-fructofuranose**.

### Final Answer:
The correct set of monosaccharides that forms sucrose is **alpha-D-glucopyranose and beta-D-fructofuranose**.

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