Non-reducing Carbohydrate

A non-reducing carbohydrate is a carbohydrate that cannot act as a reducing agent because it does not have a free aldehyde or ketone functional group. Such carbohydrates are formed by the condensation of two or more monosaccharide units with the loss of a water molecule.

Examples of Non-reducing Carbohydrates

- Sucrose: It is a disaccharide composed of glucose and fructose units. It is not a reducing sugar because the glycosidic bond between glucose and fructose units is formed between the anomeric carbons of both sugars, leaving no free reducing end.
- Lactose: It is a disaccharide composed of glucose and galactose units. It is a reducing sugar because the glycosidic bond between glucose and galactose units is formed between the anomeric carbon of glucose and the hydroxyl group of galactose, leaving a free reducing end.
- Maltose: It is a disaccharide composed of two glucose units. It is a reducing sugar because the glycosidic bond between glucose units is formed between the anomeric carbon of one glucose and the hydroxyl group of the other glucose, leaving a free reducing end.

Conclusion

Sucrose is a non-reducing carbohydrate because it does not have a free reducing end due to the formation of a glycosidic bond between the anomeric carbons of glucose and fructose units.

Non-Reducing Carbohydrate:

Carbohydrates are classified into two categories based on their reducing properties - reducing and non-reducing carbohydrates.

- Reducing Carbohydrates: These are the carbohydrates that have a free aldehyde or ketone group and can reduce other compounds like Fehling's or Benedict's reagent. Examples include glucose and fructose.
- Non-Reducing Carbohydrates: These are the carbohydrates that do not have a free aldehyde or ketone group and cannot reduce other compounds like Fehling's or Benedict's reagent. Examples include sucrose and trehalose.

Explanation:

Out of the given options, only sucrose is a non-reducing carbohydrate. Sucrose is a disaccharide composed of glucose and fructose units joined by a glycosidic bond. It does not have a free aldehyde or ketone group, and therefore cannot reduce other compounds.

On the other hand, lactose, maltose, and ribose-5-phosphate are all reducing carbohydrates. Lactose is a disaccharide composed of glucose and galactose units and can reduce Fehling's or Benedict's reagent. Maltose is a disaccharide composed of two glucose units and also has a free aldehyde group that can reduce other compounds. Ribose-5-phosphate is a monosaccharide that contains a ketone group and can also reduce other compounds.

Therefore, the correct answer is option D - Sucrose.