Which pair is an example of anomers?

Options

A. `alpha`-D-glucose and `beta`-D-glucose
B. Glucose and mannose
C. Glucose and fructose
D. Fructose and sugar

Answer

To determine which pair is an example of anomers, we need to understand the concept of anomers in carbohydrates. Anomers are a specific type of stereoisomer that differ in configuration at the anomeric carbon, which is the carbon atom that was the carbonyl carbon (C=O) in the open-chain form of the sugar.

### Step-by-Step Solution:

1. **Define Anomers**: Anomers are a type of stereoisomer that differ in configuration around the anomeric carbon (C1) in cyclic forms of sugars.

2. **Identify the Anomeric Carbon**: In the case of glucose, the anomeric carbon is the first carbon (C1) in the pyranose ring.

3. **Draw Structures**:
- **Alpha-D-Glucose**: In this form, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned below the plane of the ring.
- **Beta-D-Glucose**: In this form, the hydroxyl group (-OH) on the anomeric carbon (C1) is positioned above the plane of the ring.

4. **Compare the Structures**:
- The only difference between alpha-D-glucose and beta-D-glucose is the position of the -OH group on the anomeric carbon (C1). This difference in configuration makes them anomers.

5. **Conclusion**: Based on the above analysis, the pair of alpha-D-glucose and beta-D-glucose is an example of anomers.

### Final Answer:
The pair that is an example of anomers is **Alpha-D-Glucose and Beta-D-Glucose**.