Which of the following carbohydrate contains β-D-galactose?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Lactose
On hydrolysis, lactose gives β-D-galactose and β-D-glucose:
\( \displaystyle \underset{\text{lactose}}{\ce{C12H22O11}} + \ce{H2O} \xrightarrow{\ce{H+}} \underset{\text{galactose}}{\ce{C6H12O6}} + \underset{\text{glucose}}{\ce{C6H12O6}} \)
Maltose, amylopectin and glycogen are built from α-D-glucose units only, so lactose is the one that contains β-D-galactose.
NCERT (2026-27 edition):
Lactose
