Which of the following is a non-reducing sugar?

Options

A. Sucrose
B. Maltose
C. Lactose
D. Glucose

Answer

To determine which of the following is a non-reducing sugar, we need to understand the concept of reducing and non-reducing sugars.

### Step-by-Step Solution:

1. **Understand Reducing Sugars**:
- Reducing sugars are those that have a free aldehyde group (-CHO) or a free ketone group (C=O). These functional groups can donate electrons, which is why they are termed "reducing".

2. **Identify Common Reducing Sugars**:
- Common examples of reducing sugars include glucose, fructose, lactose, and maltose.
- Glucose has a free aldehyde group, making it a reducing sugar.
- Lactose, being a disaccharide composed of glucose and galactose, also has a free aldehyde group, hence it is a reducing sugar.
- Maltose, another disaccharide made up of two glucose units, has a free aldehyde group as well.

3. **Examine Sucrose**:
- Sucrose is a disaccharide made up of glucose and fructose. However, in sucrose, the aldehyde group of glucose and the ketone group of fructose are involved in a glycosidic bond.
- This bonding means that neither the aldehyde nor the ketone group is free, which results in sucrose lacking the ability to act as a reducing sugar.

4. **Conclusion**:
- Since sucrose does not have a free aldehyde or ketone group, it is classified as a non-reducing sugar.

### Final Answer:
The non-reducing sugar among the options provided is **sucrose**.

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