Q.8 The common component in crustacean exoskeleton and fungal cell wall is
(A) lignin (B) cellulose (C) chitin (D) peptidoglycan
The common component in crustacean exoskeleton and fungal cell wall is chitin (C).
Chitin serves as the primary structural polysaccharide in both structures, providing rigidity and protection. Crustacean exoskeletons consist mainly of chitin reinforced with proteins and minerals like calcium carbonate, while fungal cell walls feature chitin alongside β-glucans.
Option Analysis
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(A) Lignin: This complex polymer strengthens plant cell walls, particularly in wood, but does not occur in crustacean exoskeletons or fungal cell walls.
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(B) Cellulose: The main component of plant cell walls, cellulose is absent from both crustacean exoskeletons and fungal cell walls, which instead rely on chitin.
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(C) Chitin: Correct choice, as it forms the fibrous scaffold in crustacean exoskeletons (up to 70% in some shells) and the inner layer of fungal cell walls (around 3-4% interwoven with glucans).
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(D) Peptidoglycan: Exclusive to bacterial cell walls for rigidity, peptidoglycan is not present in eukaryotes like fungi or crustaceans.
Chitin stands out as the key common component in crustacean exoskeleton and fungal cell wall, making it a vital topic for biology exams like CSIR NET. This tough polysaccharide provides structural support across diverse organisms.
Chitin’s Role in Structures
Chitin, a β-(1,4)-linked N-acetylglucosamine polymer, forms the backbone of crustacean exoskeletons like those of crabs and shrimp, often comprising 17-72% of shell weight alongside proteins and minerals. In fungal cell walls, it creates a microfibrillar scaffold (3-4%) hydrogen-bonded with β-(1,3)-glucans for rigidity and shape.
Why Not Other Options?
Lignin rigidifies plant vascular tissues but skips animal and fungal structures. Cellulose defines plant walls, while peptidoglycan is bacteria-specific.
Biological Significance
Chitin enables molting in crustaceans and stress resistance in fungi, highlighting evolutionary convergence in extracellular matrices.
