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Questions and Answers
What are the three stages of peptidoglycan synthesis?
What are the three stages of peptidoglycan synthesis?
Which gene is NOT involved in the pathway of peptidoglycan synthesis in E.coli?
Which gene is NOT involved in the pathway of peptidoglycan synthesis in E.coli?
What is the role of phosphonomycin in peptidoglycan synthesis?
What is the role of phosphonomycin in peptidoglycan synthesis?
Which of the following statements is NOT a general step in peptidoglycan biosynthesis?
Which of the following statements is NOT a general step in peptidoglycan biosynthesis?
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Which two antibiotics act at the first step of the peptidoglycan synthesis cascade?
Which two antibiotics act at the first step of the peptidoglycan synthesis cascade?
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What is the primary component of the cell walls in vascular plants?
What is the primary component of the cell walls in vascular plants?
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Which polymer is predominantly found in the cell walls of fungi?
Which polymer is predominantly found in the cell walls of fungi?
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What is the composition percentage of β-glycans in the yeast cell wall of S.cerevisiae?
What is the composition percentage of β-glycans in the yeast cell wall of S.cerevisiae?
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What is the term used for the rigid structure that forms the major backbone of bacterial cell walls?
What is the term used for the rigid structure that forms the major backbone of bacterial cell walls?
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What type of cell wall structure is unique to archaea as compared to bacteria?
What type of cell wall structure is unique to archaea as compared to bacteria?
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What characterizes the cell wall of gram-negative bacteria such as E.coli?
What characterizes the cell wall of gram-negative bacteria such as E.coli?
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Which of the following components is found in smaller percentages in the yeast cell wall?
Which of the following components is found in smaller percentages in the yeast cell wall?
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What primary role do the cell walls of microorganisms serve?
What primary role do the cell walls of microorganisms serve?
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What is one key function of the bacterial cell wall?
What is one key function of the bacterial cell wall?
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Which component is primarily responsible for the strength of the bacterial cell wall?
Which component is primarily responsible for the strength of the bacterial cell wall?
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What are the two sugar derivatives that form peptidoglycan?
What are the two sugar derivatives that form peptidoglycan?
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How does the bacterial cell wall prevent bursting due to osmosis?
How does the bacterial cell wall prevent bursting due to osmosis?
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What kind of amino acids are connected in peptidoglycan to form the glycan tetrapeptide?
What kind of amino acids are connected in peptidoglycan to form the glycan tetrapeptide?
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Why are glycosidic bonds formed in peptidoglycan important?
Why are glycosidic bonds formed in peptidoglycan important?
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In Gram-negative bacteria, how does cross-linking usually occur?
In Gram-negative bacteria, how does cross-linking usually occur?
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What characteristic does the cell wall contribute to regarding bacterial pathogenicity?
What characteristic does the cell wall contribute to regarding bacterial pathogenicity?
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Which amino acids are never found in the interbridge of peptidoglycan?
Which amino acids are never found in the interbridge of peptidoglycan?
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What role does peptidoglycan play in bacteria?
What role does peptidoglycan play in bacteria?
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Which antibacterial drug inhibits the synthesis of peptidoglycan?
Which antibacterial drug inhibits the synthesis of peptidoglycan?
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What triggers programmed cell death in bacteria?
What triggers programmed cell death in bacteria?
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What is the function of glycan-strand hydrolyzing peptidoglycan hydrolases?
What is the function of glycan-strand hydrolyzing peptidoglycan hydrolases?
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Which of the following enzymes is classified as an endopeptidase hydrolyzing?
Which of the following enzymes is classified as an endopeptidase hydrolyzing?
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What is N-acetylmuramic acid's significance in bacteria?
What is N-acetylmuramic acid's significance in bacteria?
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What important role do peptidoglycan hydrolases play during cell growth?
What important role do peptidoglycan hydrolases play during cell growth?
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What primarily makes up the cell wall of gram-positive bacteria?
What primarily makes up the cell wall of gram-positive bacteria?
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Which amino acid is found in the interbridge of the peptidoglycan structure in Staphylococcus aureus?
Which amino acid is found in the interbridge of the peptidoglycan structure in Staphylococcus aureus?
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What is the predominant sugar component found in the glycan portion of peptidoglycan?
What is the predominant sugar component found in the glycan portion of peptidoglycan?
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Which component is typically absent in the cell walls of Archaea?
Which component is typically absent in the cell walls of Archaea?
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What percentage of the cell wall in gram-negative bacteria consist of peptidoglycan?
What percentage of the cell wall in gram-negative bacteria consist of peptidoglycan?
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What type of linkage connects the sugars in the glycan portion of peptidoglycan?
What type of linkage connects the sugars in the glycan portion of peptidoglycan?
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Which amino acid is involved in the lysine-diaminopimelic acid alternation within the tetrapeptide of peptidoglycan?
Which amino acid is involved in the lysine-diaminopimelic acid alternation within the tetrapeptide of peptidoglycan?
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How many different peptidoglycan types are known?
How many different peptidoglycan types are known?
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Study Notes
Cell Wall Structure and Functions
- The cell wall exists outside the cell membrane in organisms like plants, fungi, bacteria, algae, and archaea.
- In vascular plants, cell walls are primarily made of cellulose, a β-1,4-linked polymer of glucose.
- Yeast cell walls exhibit a layered structure; they contain 29% β-glycans, 31% mannan, and 13% protein.
Prokaryotic Cell Surfaces
- Peptidoglycan serves as the main structural component of bacterial cell walls, providing rigidity.
- Archaea have a unique structure called pseudomurein along with protein or glycoprotein-based S-layer.
- Gram-positive bacteria may have up to 90% of their cell walls composed of peptidoglycan, while in gram-negative bacteria, it is about 10%.
Peptidoglycan Structure
- Peptidoglycan is composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), along with certain amino acids.
- Glycosidic bonds between sugars in glycan chains provide strength, but rigidity is enhanced by amino acid cross-linking.
- Cross-linking varies between species; Gram-positive bacteria typically have peptide interbridges, while Gram-negative exhibit direct linkage.
Peptidoglycan Synthesis and Antibiotic Targets
- Peptidoglycan synthesis has three main stages: cytoplasmic (precursor synthesis), membrane (precursor transport), and extracellular (cross-linking).
- Important genes in E. coli for peptidoglycan synthesis include murC, murD, murE, ddl, murF, mraY, and murG.
- Antibiotics like penicillin and vancomycin inhibit transpeptidase, preventing cross-link formation.
Peptidoglycan Hydrolases
- Almost all bacteria produce peptidoglycan hydrolases, essential for various cellular activities such as cell growth and wall turnover.
- These enzymes include endo-N-acetylmuramidases, endo-N-acetylglucosaminidases, and endopeptidases, critical in maintaining cell integrity.
- Activation of hydrolases under stress can lead to programmed cell death, also known as apoptosis.
Antibiotic Mechanisms
- Phosphonomycin and cycloserine inhibit the first step in peptidoglycan synthesis by blocking the biosynthesis of UDP muramic acid.
- These antibiotics target the synthesis pathway at different stages, making peptidoglycan a viable target for treatment.
Important Concepts
- The characteristic cell shape and osmotic resilience of bacteria are largely determined by peptidoglycan structure.
- Peptidoglycan is unique to bacteria, making it an effective target for antibacterial agents, posing no harm to human cells.
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Description
This quiz focuses on the structure and properties of the cell wall, particularly the peptidoglycan cell wall synthesis, function, and its importance in microbial physiology. It also highlights how the bacterial cell wall serves as a target for antibiotic treatments. Test your understanding of these critical concepts in biology.
