9.

Question 1

role of the cell wall

Answer 1

• prevents cell expansion- protects against osmotic lysis
• protects agains toxic substances-large hydrophobic molecules
• pathogenicity-helps evade host immune system
  - helps bacterium stick to surfaces
• partly responsible for cell shape

Question 2

peptidoglycan

Answer 2

• species of bacteria separated into two groups based on gram stain
• gram +ive and gram -ive have different cell wall structure

Question 3

Gram negative cell wall

Answer 3

two layers LPS and peptidoglycan
-LPS forms part of outer membrane
(outer membrane, peptidoglycan, inner membrane)

Question 4

gram positive cell wall

Answer 4

one layer peptidoglycan

peptidoglycan, inner membrane

Question 5

peptidoglycan structure

Answer 5

• rigid layer that provides strength to the cell wall
• more than 100 different structures identified
• vary in peptide cross-links and/or inter-bridge
• No inter-bridge is present in gram negative bacteria (e. coli)
• the inter-bridge in staphylococcus aureus gram +ve is made up of 5 glycine residues

Question 6

peptidoglycan polysaccharide composed of

Answer 6

• N-acetylglucosamine and N-acetylmuramic acid
• amino acids
• lysine or diaminopilmelic acid (DAP)
• cross linked differently in gram negative bacteria and gram positive bacteria
• form glycan tetrapeptide

Question 7

N-acetylglucosamine (G) and n-acetylmuramic acid (m) has what type of bonds:

Answer 7

beta (1,4)

Question 8

gram positive cell walls

Answer 8

• contain up to 90% PG
• common to have teichoic acids ( acidic substances)
• embedded in their cell wall
  
  • lipoteichoic acids: teichoic acids covalently bound to membrane lipids

Question 9

Model of peptidoglycan surround the cell

Answer 9

• backbone formed of NAM and NAG connected by glycosidic bonds
• crosslinks formed by peptides
• peptidoglycan strand is helical- allows 3D crosslinking
• E.coli has one layer
• some cell walls can be 50-100 layers thick, eg bacillus speices

Question 10

prokaryotes that lack cell walls

Answer 10

mycoplasmas

thermoplasma

Question 11

mycoplasmas

Answer 11

group of pathogenic bacteria

have sterols in cytoplasmic membrane- adds strength and rigidity to membrane

Question 12

thermoplasma

Answer 12

• species of archaea

- contain lipoglycans in membrane that have strengthening effect

Question 13

cell walls of bacteria and archaea

Answer 13

outside the cell membrane

• cell wall
• rigid-helps determine cell shape
• not a major permeability barrier
• porous to most small molecules
• protects the cell from osmotic changes