Question:
The repeating unit in the polysaccharide component of peptidoglycans present in the bacterial cell wall is a
The repeating unit in the polysaccharide component of peptidoglycans present in the bacterial cell wall is a
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Peptidoglycan structure consists of a glycan backbone and a peptide cross-link.
The glycan backbone is a polymer of the repeating disaccharide unit: N-acetylglucosamine (NAG) linked to N-acetylmuramic acid (NAM).
The glycan backbone is a polymer of the repeating disaccharide unit: N-acetylglucosamine (NAG) linked to N-acetylmuramic acid (NAM).
Updated On: Aug 7, 2026
- Disaccharide
- Monosaccharide
- Trisaccharide
- Tetrasaccharide
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Peptidoglycan (also known as murein) is a complex polymer that forms a protective mesh-like layer outside the plasma membrane of most bacteria, constituting the primary structural component of the cell wall.
It consists of glycan chains cross-linked by short peptide bridges.
Step 2: Detailed Explanation:
The glycan portion of the peptidoglycan molecule consists of a linear chain of alternating amino sugars.
These two monosaccharide derivatives are:
1. N-acetylglucosamine (NAG)
2. N-acetylmuramic acid (NAM)
These sugars are linked together through $\beta$-(1,4)-glycosidic bonds.
Because the polymer is built from alternating NAG and NAM units, the fundamental repeating unit of this polysaccharide backbone is a disaccharide (NAG-NAM).
Short tetrapeptide chains are covalently attached to the lactic acid group of the NAM residues.
These peptide chains are further cross-linked to adjacent glycan strands, providing the cell wall with high mechanical strength and resistance to osmotic pressure.
Step 3: Final Answer:
The repeating unit in the polysaccharide component of peptidoglycan is a disaccharide, which corresponds to Option (A).
Peptidoglycan (also known as murein) is a complex polymer that forms a protective mesh-like layer outside the plasma membrane of most bacteria, constituting the primary structural component of the cell wall.
It consists of glycan chains cross-linked by short peptide bridges.
Step 2: Detailed Explanation:
The glycan portion of the peptidoglycan molecule consists of a linear chain of alternating amino sugars.
These two monosaccharide derivatives are:
1. N-acetylglucosamine (NAG)
2. N-acetylmuramic acid (NAM)
These sugars are linked together through $\beta$-(1,4)-glycosidic bonds.
Because the polymer is built from alternating NAG and NAM units, the fundamental repeating unit of this polysaccharide backbone is a disaccharide (NAG-NAM).
Short tetrapeptide chains are covalently attached to the lactic acid group of the NAM residues.
These peptide chains are further cross-linked to adjacent glycan strands, providing the cell wall with high mechanical strength and resistance to osmotic pressure.
Step 3: Final Answer:
The repeating unit in the polysaccharide component of peptidoglycan is a disaccharide, which corresponds to Option (A).
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