Which one of the following is non-reducing sugar ?

Options

A. Glucose
B. Mannose
C. Fructose
D. Sucrose

Explanation

To determine which of the following sugars is a non-reducing sugar, we will analyze the structures of the given sugars and identify their functional groups.

### Step 1: Understand the definition of reducing and non-reducing sugars.
Reducing sugars are those that can donate electrons to another chemical, thus reducing it. They typically contain free aldehyde or ketone groups. Non-reducing sugars do not have these functional groups and therefore do not participate in redox reactions.

### Step 2: Identify the sugars in the question.
The common sugars to consider are:
- Glucose
- Mannose
- Fructose
- Sucrose

### Step 3: Draw and analyze the structures of each sugar.
1. **Glucose**:
- Contains an aldehyde group (CHO).
- Structure: C6H12O6 (open-chain form has CHO at one end).

2. **Mannose**:
- Similar to glucose, it also contains an aldehyde group (CHO).
- Structure: C6H12O6 (open-chain form has CHO at one end).

3. **Fructose**:
- Contains a ketone group (C=O) in its structure.
- Structure: C6H12O6 (open-chain form has a ketone group).

4. **Sucrose**:
- Composed of glucose and fructose linked together.
- Does not have a free aldehyde or ketone group in its structure.
- Structure: C12H22O11 (no CHO or C=O groups present).

### Step 4: Determine which sugars are reducing or non-reducing.
- **Glucose**: Reducing sugar (has CHO group).
- **Mannose**: Reducing sugar (has CHO group).
- **Fructose**: Reducing sugar (has C=O group).
- **Sucrose**: Non-reducing sugar (no free aldehyde or ketone groups).

### Conclusion:
The non-reducing sugar among the options is **Sucrose**.

### Final Answer:
**Sucrose is the non-reducing sugar.**

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