What are the two monosaccharides which are obtained by hydrolysis of lactose sugar?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → D-(+)- Glucose and D-(+)-Galactose
Lactose is a disaccharide (milk sugar) composed of one molecule of D-glucose and one molecule of D-galactose, linked by a β-1,4-glycosidic bond. Hydrolysis (acid-catalyzed or enzymatic via lactase) breaks this bond, yielding these two monosaccharides.
Explanation of options:
- D-(+) Fructose and D-(+)-Galactose — Incorrect (sucrose yields glucose + fructose).
- D-(+)- Maltose and D-(+)-Galactose — Incorrect (maltose is a disaccharide itself, yielding two glucose molecules).
- D-(+)- Glucose and D-(+)-Galactose — Correct.
- D-(+) Maltose and D-(+) - Fructose — Incorrect (no relation to lactose).