Question

Lactose is a disaccharide present in milk. It comprises of

• A. \( \beta - D \)-Galactose and \( \beta - D \)-Glucose
• B. \( \alpha - D \)-Galactose and \( \beta - D \)-Glucose
• C. \( \beta - D \)-Glucose and \( \beta - D \)-Fructose
• D. \( \beta - D \)-Glucose and \( \alpha - D \)-Glucose

Hint:

In disaccharides like lactose, pay attention to the anomeric configurations of the constituent monosaccharides, which play a crucial role in their structure and properties.

Answer 1

The Correct Option is B

Lactose is a disaccharide composed of two monosaccharides: glucose and galactose. Specifically, it is formed by the condensation of one molecule of \( \alpha - D \)-Galactose and \( \beta - D \)-Glucose. In lactose, the glucose unit is in the \( \beta \)-configuration, while the galactose is in the \( \alpha \)-configuration, which is characteristic of lactose.
Thus, the correct combination is \( \alpha - D \)-Galactose and \( \beta - D \)-Glucose.