Question

Lactose is made of:

• A. $\alpha -D$-glucose only
• B. $\alpha -D$-glucose only and $\beta -D$-glucose
• C. $\alpha -D$-galactose and $\beta -D$-glucose
• D. $\beta -D$-galactose and $\beta -D$-glucose

Answer 1

The correct option is D $\beta -D$-galactose and $\beta -D$-glucose

Lactose is made up of $-\beta -D-$ galactopyranosyl$-(1\to 4)-D-$ glucose. Hence answer D is correct.

Although, glucose can be in alpha or beta anomeric form and that will decide the alpha or beta Lactose. But since only lactose, in general, has been asked then answer D is correct.