Q.27 N-acetylglucosamine (NAG) and N- acetylmuramic acid (NAM) in cell wall
of bacteria are connected by:
1. ß-1,4 glycosidic bond
2. ß-1,2 glycosidic bond
3. ß-1,3 glycosidic bond
4. ß-2,4 glycosidic bond
N-Acetylglucosamine and N-Acetylmuramic Acid Linkage in Bacterial Cell Walls
N-acetylglucosamine (NAG, or GlcNAc) and N-acetylmuramic acid (NAM, or MurNAc) form the repeating disaccharide backbone of bacterial peptidoglycan, connected by β-1,4 glycosidic bonds. This linkage provides structural rigidity to the cell wall in both Gram-positive and Gram-negative bacteria.
Correct Answer
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β-1,4 glycosidic bond
Option Breakdown
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1. β-1,4 glycosidic bond: Correct. The peptidoglycan chain alternates as …-NAM-(β-1,4)-NAG-(β-1,4)-NAM-…, synthesized by glycosyltransferases during cell wall assembly.
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2. β-1,2 glycosidic bond: Incorrect. β-1,2 linkages are rare in bacterial polysaccharides and not found in peptidoglycan backbones.
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3. β-1,3 glycosidic bond: Incorrect. These occur in fungal chitin (GlcNAc polymers) or some bacterial capsules, but not peptidoglycan.
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4. β-2,4 glycosidic bond: Incorrect. No such standard glycosidic linkage exists; peptidoglycan uses C1-to-C4 β-glycosidic bonds exclusively.
| Option | Bond Type | Used in Peptidoglycan? | Common In |
|---|---|---|---|
| 1 | β-1,4 | Yes | Bacterial cell walls |
| 2 | β-1,2 | No | Rare polysaccharides |
| 3 | β-1,3 | No | Fungal chitin |
| 4 | β-2,4 | No | None |
