Q.41 Which of the following carbohydrates has/have a 𝛽1 → 4 glycosidic linkage?
(A) Cellulose
(B) Chitin
(C) Lactose
(D) Maltose
Cellulose, chitin, and lactose contain β1→4 glycosidic linkages, while maltose has an α1→4 linkage, making options (A), (B), and (C) correct for this CSIR NET Life Sciences question.
Detailed Option Breakdown
Cellulose features linear chains of β-D-glucose linked by β1→4 glycosidic bonds between C1 of one unit and C4 of the next, forming rigid microfibrils via hydrogen bonding in plant cell walls.
Chitin consists of N-acetyl-β-D-glucosamine units connected by β1→4 linkages, providing structural strength in fungal cell walls and arthropod exoskeletons through similar hydrogen-bonded sheets.
Lactose links β-D-galactose (C1) to D-glucose (C4) via a β1→4 glycosidic bond, a key disaccharide in milk hydrolyzed by β-galactosidase.
Maltose joins two α-D-glucose molecules through an α1→4 glycosidic bond, enabling flexible helical structures unlike the linear β-linked polymers.
Structural Comparison
| Carbohydrate | Monomer(s) | Linkage Type | Function | Digestibility in Humans |
|---|---|---|---|---|
| Cellulose (A) | β-D-Glucose | β1→4 | Plant cell walls | No (lacks cellulase) |
| Chitin (B) | N-acetyl-β-D-Glucosamine | β1→4 | Exoskeletons, fungal walls | Partial |
| Lactose (C) | β-D-Galactose + D-Glucose | β1→4 | Milk sugar | Yes (lactase) |
| Maltose (D) | α-D-Glucose (x2) | α1→4 | Starch breakdown product | Yes (maltase) |
β1→4 linkages produce extended, straight chains resistant to human enzymes, contrasting α linkages that form coils for energy storage.
