Bacteria: Structure and Pathogenesis · USMLE Step 1

Which structural component is unique to bacterial cell walls and helps maintain their shape against osmotic pressure?

  1. Chitin
  2. Cellulose
  3. Peptidoglycan
  4. Keratin
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Correct answer: Peptidoglycan

Peptidoglycan (murein) is unique to bacteria and forms a mesh-like layer that provides rigidity and protects against osmotic stress. It consists of alternating N-acetylglucosamine and N-acetylmuramic acid chains cross-linked by peptide bridges.

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