Which is a reducing sugar ?

Options

A. Cellulose
B. Maltose
C. Sucrose
D. Starch

Answer

To determine which sugar is a reducing sugar, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Reducing Sugar**:
- A reducing sugar is a type of sugar that has a free aldehyde or ketone group. This functional group allows the sugar to act as a reducing agent.

2. **Categorize Sugars**:
- Sugars can be classified into two categories: reducing sugars and non-reducing sugars.
- Reducing sugars include monosaccharides and some disaccharides, while non-reducing sugars do not have a free aldehyde or ketone group.

3. **Identify Common Reducing Sugars**:
- Monosaccharides such as glucose and fructose are reducing sugars.
- Disaccharides such as maltose and lactose are also reducing sugars.

4. **Identify Non-Reducing Sugars**:
- Non-reducing sugars include sucrose (a disaccharide) and polysaccharides like starch and cellulose.

5. **Conduct a Test for Reducing Sugars**:
- The Fehling's test or Benedict's test can be used to identify reducing sugars. In these tests, a blue copper sulfate solution is used, which changes color to red when a reducing sugar is present.

6. **Evaluate the Options**:
- If given options, identify which sugars are reducing based on the above classifications. For example, if the options include maltose, sucrose, cellulose, and starch, we can determine that maltose is a reducing sugar.

### Conclusion:
Based on the classifications and tests, the answer to the question "Which is a reducing sugar?" is **Maltose**.

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