Question

Lactose is disaccharide containing ________.

• A. Glucose and Fructose
• B. Glucose and Glactose
• C. Glucose and Glucose
• D. Glucose and Maltose

Hint:

To remember the three main disaccharides: - Sucrose = Glucose + Fructose.
- Maltose = Glucose + Glucose.
- Lactose = Glucose + Galactose (milk sugar).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Disaccharides are carbohydrates composed of two monosaccharide units linked together by a glycosidic bond.
Detailed Explanation:
Lactose is the primary sugar found naturally in mammalian milk.
- It is a disaccharide composed of one D-glucose molecule and one D-galactose molecule linked by a $\beta$-1,4-glycosidic bond.
- It is hydrolyzed in the digestive tract by the enzyme lactase ($\beta$-galactosidase) into its constituent monosaccharides for absorption.
Let us review the other options:
- Glucose + Fructose (A): Forms Sucrose (table sugar).
- Glucose + Glucose (C): Forms Maltose (malt sugar, linked by an $\alpha$-1,4-bond) or Cellobiose (linked by a $\beta$-1,4-bond).
- Glucose + Maltose (D) is not a standard disaccharide.

Step 2: Final Answer:
Lactose is a disaccharide made of glucose and galactose, corresponding to option (B).