Question

Identify the glycosidic linkage present in lactose.

• A. $\alpha - 1, 6$
• B. $\alpha - 1, 4$
• C. $\beta - 1, 4$
• D. $\alpha, \beta - 1, 2$

Hint:

Remember the carbohydrate connection map: $\text{Maltose} \rightarrow \alpha$-1,4 linkage $\text{Lactose} \rightarrow \beta$-1,4 linkage $\text{Sucrose} \rightarrow \alpha$-1, $\beta$-2 linkage A quick mnemonic: Lactose has a "$\beta$"etter connection for milk!

Answer 1

The Correct Option is C

Step 1: Break down lactose.
Lactose is built from galactose and glucose joined together.

Step 2: Find the link.
The bond forms between C1 of galactose, in the beta form, and C4 of glucose. That makes it a beta 1,4 linkage.

Step 3: Confirm against others.
Maltose has alpha 1,4 and sucrose has alpha,beta 1,2, so lactose stands out as beta 1,4.
\[ \boxed{\beta\text{-}1,4,\ \text{option 3}} \]