Question

Identify glycosidic linkage in lactose.

• A. \(α-1,4\)
• B. \(β-1,4\)
• C. \(α-1,6\)
• D. \(β-2,6\)

Hint:

Lactose is galactose joined to glucose through a beta-1,4 glycosidic bond.

Answer 1

The Correct Option is B

Step 1: Identify the units:
Hydrolysis of lactose gives D-galactose and D-glucose in equal amounts.

Step 2: Locate the bond:
The C1 of galactose in its beta form joins through an oxygen bridge to C4 of glucose. This is a $\beta$-1,4 linkage.

Step 3: Compare:
Maltose, with two glucose units, has the $\alpha$-1,4 link of option (A). The $\alpha$-1,6 link of option (C) is the branch point in amylopectin. A $\beta$-2,6 link is not seen in lactose.

Final Answer:
Option (B). \[ \boxed{\beta\text{-1,4 (B)}} \]