Question

The glycosidic bond between the monomers of sucrose is-

• A. Gal(1\(\beta \rightarrow \beta\)4)Glc
• B. Fru(4\(\beta \rightarrow \beta\)1)Glc
• C. Fru(4\(\beta \rightarrow \alpha\)2)Glc
• D. Fru(2\(\beta \leftrightarrow \alpha\)1)Glc

Hint:

Sucrose is unique because its glycosidic bond involves the anomeric carbons of both sugar units. This locks them and makes sucrose a non-reducing sugar. Remember the linkage: \(\alpha\)-1 (glucose) to \(\beta\)-2 (fructose).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Sucrose is a non-reducing disaccharide composed of two monosaccharides: glucose and fructose. A glycosidic bond links these two monomers. We need to identify the specific nature of this bond.
Step 2: Detailed Explanation:


The monomers of sucrose are \(\alpha\)-D-glucose and \(\beta\)-D-fructose.

The glycosidic bond is formed between the anomeric carbon of glucose (C1) and the anomeric carbon of fructose (C2).

Specifically, the linkage is from the C1 of \(\alpha\)-glucose to the C2 of \(\beta\)-fructose.

The systematic name is \(\alpha\)-D-glucopyranosyl-(1\(\rightarrow\)2)-\(\beta\)-D-fructofuranoside.

Let's analyze the options:

(A) describes the bond in lactose (Galactose + Glucose).

(B) and (C) show incorrect linkages and carbons.

(D) Fru(2\(\beta \leftrightarrow \alpha\)1)Glc correctly represents the bond between the C1 of \(\alpha\)-glucose and the C2 of \(\beta\)-fructose. The double arrow (\(\leftrightarrow\)) is often used to indicate a bond between two anomeric carbons, which is why sucrose is a non-reducing sugar.


Step 3: Final Answer:
The glycosidic bond in sucrose is an \(\alpha\)-1, \(\beta\)-2 linkage between glucose and fructose, correctly represented by option (D).