Which of the following is reducing and non-reactive sugar ?

Options

A. Galactose
B. Gluconic acid
C. Methygalactoside
D. Sucrose

Answer

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

### Step-by-Step Solution:

1. **Definition of Reducing Sugar**:
- Reducing sugars are those that have a free aldehyde or free ketone group. These functional groups can donate electrons to other molecules, thus reducing them. Common examples include glucose and galactose.

**Hint**: Look for sugars with free aldehyde or ketone groups.

2. **Definition of Non-Reactive Sugar**:
- Non-reactive sugars do not participate in reactions such as the Benedict's test, which is used to identify reducing sugars. If a sugar does not react in this test, it is considered non-reactive.

**Hint**: Non-reactive sugars do not change during the Benedict's test.

3. **Identifying the Options**:
- We need to evaluate the options provided (Galactose, Gluconic acid, Methyl Galactosidase, and Sucrose) to see which one fits the criteria of being both reducing and non-reactive.

4. **Analysis of Each Sugar**:
- **Galactose**: It has a free aldehyde group (CHO) and is a reducing sugar. However, it is mentioned that it does not give a positive result in the Benedict's test, making it non-reactive.
- **Gluconic Acid**: This is a non-reducing sugar because it does not have a free aldehyde or ketone group.
- **Methyl Galactosidase**: This is also a non-reducing sugar and will not react in the Benedict's test.
- **Sucrose**: This is a well-known non-reducing sugar as it does not have a free aldehyde or ketone group.

5. **Conclusion**:
- Among the options, **Galactose** is the only sugar that is reducing (due to its free aldehyde group) and non-reactive (does not give a positive result in the Benedict's test).

### Final Answer:
The correct option is **Galactose**, which is a reducing and non-reactive sugar.