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Questions and Answers
What is the primary chemical structure of peptidoglycans comprised of?
What is the primary chemical structure of peptidoglycans comprised of?
- A branched chain of fatty acids
- A linear chain of amino acids
- A glycan backbone of β1,4-linked disaccharides (correct)
- A polysaccharide of glucose and fructose
What role do specific enzymes play in prokaryotic cells?
What role do specific enzymes play in prokaryotic cells?
- They degrade the cell wall.
- They transport nutrients into the cell.
- They are responsible for peptidoglycan synthesis. (correct)
- They enhance the speed of ATP production.
In the peptidoglycan structure of S.aureus, what connects the two adjacent peptide structures?
In the peptidoglycan structure of S.aureus, what connects the two adjacent peptide structures?
- A glycine pentapeptide bridge (correct)
- A disulfide bridge
- A hydrogen bond
- A carboxyl linkage
Which characteristic differentiates the peptidoglycan of S.aureus from that of E.coli?
Which characteristic differentiates the peptidoglycan of S.aureus from that of E.coli?
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What is the diamino acid always present in Gram-negative peptidoglycans for cross-linking?
What is the diamino acid always present in Gram-negative peptidoglycans for cross-linking?
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Study Notes
Peptidoglycan Structure and Synthesis
- Nearly all prokaryotes, excluding Halobacterium halobium and mycoplasmas, have a cell wall composed of peptidoglycan.
- This unique structure is targeted by specific antibiotics, which inhibit the enzymes responsible for peptidoglycan synthesis.
- Peptidoglycan in both Gram-positive and Gram-negative bacteria consists of a glycan backbone made up of repeating units of β1,4-linked disaccharides of β1,4-N-acetylmuramyl-N-acetylglucosamine.
- Tetrapeptides of L-alanine-D-isoglutamic acid-L-lysine (or diaminopimelic acid)-n-alanine are attached to the muramic acid residues of the glycan chains.
- Crosslinking between tetrapeptides occurs either directly through the D-alanine residues or via a peptide bridge, linking them to the 𝛆-amino group of lysine or diaminopimelic acid in a neighboring tetrapeptide.
- Staphylococcus aureus peptidoglycan features a glycine pentapeptide bridge connecting adjacent peptide structures.
- The degree of crosslinking varies between different peptidoglycans, with Staphylococcus aureus exhibiting high crosslinking and Escherichia coli having a more open mesh structure with less crosslinking.
- Diaminopimelic acid or lysine serves as the 𝛆-amino group donor for cross-linking in Gram-negative peptidoglycans.
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