Which one of the following is a non-reducing carbohydrate?

Options

A. Ribose 5-phosphate
B. Malotose
C. Sucrose
D. Lactose

Answer

To determine which of the following carbohydrates is a non-reducing carbohydrate, we will analyze each option provided: ribose 5-phosphate, maltose, sucrose, and lactose.

### Step-by-Step Solution:

1. **Understanding Non-Reducing Carbohydrates**:
- Non-reducing carbohydrates are those that cannot be oxidized by weak oxidizing agents. This is primarily because they lack certain functional groups, specifically the aldehyde (CHO) or ketone (C=O) groups that are necessary for oxidation.

2. **Identifying the Functional Groups**:
- Carbohydrates with free aldehyde or ketone groups can be oxidized and are termed reducing sugars. Non-reducing sugars do not have these functional groups available.

3. **Analyzing Each Option**:
- **Ribose 5-Phosphate**: Ribose is a pentose sugar that contains an aldehyde group, thus it is a reducing sugar.
- **Maltose**: Maltose is a disaccharide made of two glucose units and has a free aldehyde group, making it a reducing sugar.
- **Sucrose**: Sucrose is a disaccharide composed of glucose and fructose. It does not have a free aldehyde or ketone group because the glycosidic bond formed between glucose and fructose involves the anomeric carbons of both sugars. Therefore, sucrose is a non-reducing sugar.
- **Lactose**: Lactose is a disaccharide made of glucose and galactose, and it contains a free aldehyde group, making it a reducing sugar.

4. **Conclusion**:
- Among the options given, sucrose is the only non-reducing carbohydrate because it lacks the necessary functional groups for oxidation.

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