Question

Lactose is composed of:

• A. \( \alpha \)-D glucose and \( \beta \)-D fructose
• B. \( \beta \)-D glucose and \( \beta \)-D galactose
• C. 2 units of \( \alpha \)-D glucose
• D. 2 units of \( \beta \)-D glucose
• E. \( \alpha \)-D glucose and \( \beta \)-D galactose

Hint:

Lactose is made from one molecule each of \( \alpha \)-D glucose and \( \beta \)-D galactose, commonly found in milk.

Answer 1

Answer: (E)

Lactose is a disaccharide composed of two monosaccharides, \( \alpha \)-D glucose and \( \beta \)-D galactose. These two monosaccharides are linked by a glycosidic bond, making lactose the sugar commonly found in milk. Step 1: Understand the composition of lactose.
Lactose is made by combining one molecule of \( \alpha \)-D glucose and one molecule of \( \beta \)-D galactose. Thus, the correct composition is \( \alpha \)-D glucose and \( \beta \)-D galactose.
Step 2: Conclusion.
Therefore, the correct answer is option (E).
Final Answer: (E) \( \alpha \)-D glucose and \( \beta \)-D galactose