Q.11 Cellulose is an unbranched polymer of glucose residues joined by
- α-1, 4 linkage
- α-1, 6 linkage
- β-1, 4 linkage
- β-1, 6 linkage
Correct Answer: β-1, 4 linkage
Cellulose forms straight, rigid chains in plant cell walls due to this specific bond between glucose units.
Option Analysis
α-1, 4 linkage
This bond creates helical structures, as seen in starch (amylose), allowing easy enzymatic breakdown for energy storage. Cellulose requires linear rigidity, so this option is incorrect.α-1, 6 linkage
Found at branch points in glycogen or amylopectin, enabling compact storage. Cellulose is unbranched and linear, ruling this out.β-1, 4 linkage
Glucose residues link C1 of one to C4 of the next in β configuration, flipping units 180° for hydrogen bonding and strength. This is the correct structure for cellulose.β-1, 6 linkage
Rare in major polysaccharides; forms different polymers like galactan, not cellulose’s tough microfibrils. Incorrect here.Cellulose, an unbranched polymer of glucose residues joined by β-1,4 linkage, forms the backbone of plant cell walls. This cellulose unbranched polymer of glucose β-1,4 linkage structure provides tensile strength unmatched by other polysaccharides. Ideal for molecular biology and botany students preparing for competitive exams.
Molecular Structure
D-Glucose units connect via β-1,4 glycosidic bonds: the anomeric C1 (β orientation) bonds to C4 of the next monomer. This inverts ring orientation every unit, enabling inter-chain H-bonds into microfibrils. Unlike α bonds, β configuration prevents coiling.
Why β-1,4 Over Others?
Linkage Type Polymer Example Key Feature Why Not Cellulose? α-1,4 Amylose (starch) Helical, digestible Too flexible; no rigidity α-1,6 Glycogen branches Compact storage Branched; not linear β-1,4 Cellulose Linear, fibrous Correct: Strong H-bonds β-1,6 Laminarin Soluble, short chains Lacks extended strength This table highlights cellulose unbranched polymer of glucose β-1,4 linkage uniqueness for structural roles.
Biological Role
In plants, cellulose microfibrils resist tension, enabling growth. Humans lack cellulase, so it acts as insoluble fiber. Industrially, it’s sourced for paper, textiles. Exam tip: Remember β for “beta-strong” plant walls vs. α for “alpha-energy” storage.
