Exam 3: Antibiotics that act on cell wall

Question 1

3 types of bacteria based on outer membrane

Answer 1

• • All cell walls made of peptidoglycans**
• gram pos: wall exposed
• gram negative: wall in between two membranes
• acid fast gram positive: mycotic acids face outside (do not have phospho heads pointing towards outside, lipid chains do)

Question 2

All antibiotics working on cell wall biosynth of gram negative must reach where to be affective?

Answer 2

• periplasm (inside first membrane, outside cell wall

Question 3

Point of peptidoglycan wall?

Answer 3

• provides structural rigidity and protection

- if inhibit this synthesis, osmotic pressure is too great and contents will leak out and bacteria will die

Question 4

Differences and similarities between G(+) and G (-) regarding wall and peptidoglycan steps

Answer 4

• differences: gram (-) very thin wall, gram (+) thick multi-layer wall
• transglycosylation and transpeptidation steps the same

Question 5

which harder to treat? gram (-) or (+)

Answer 5

• gram (-) harder

Question 6

gram (-) have what on outer membrane that penicillin can get through (but not vancomycin)?

Answer 6

• porin

- penicillin is small enough

Question 7

Fosfomycin

Answer 7

• works in cytoplasm
• works on first step in PG biosynth
• inihibits MurA, mimics PEP

Question 8

lipid synthesis I inhibitors are _____

Answer 8

• still under development/ not used in clinic

Question 9

Vancomycin

Answer 9

• glycopeptide
• works in periplasm
• inhibits TGase (transglycolase) (elongation step)
• only works Gram (+), too big to get through gram (-) outer membrane

Question 10

Penicillins

Answer 10

• B-lactam (first line antibiotic class)
• works in periplasm
• inhibits TPase (transpeptidase) (cross-linking/ transpeptidation step)
• some requirement to get through membrane with gram (-) none with gram (+_

Question 11

Cephalosporins

Answer 11

• B-lactam (first line antibiotic class)
• work in periplasm
• block transpeptidation step by blocking TPase
• gram (-) some requirement to get through membrane, gram (+) no requirement