antibiotics med chem Flashcards
(97 cards)
mutualistic relationship
both organisms benefit
opportunistic relationship
under normal conditions the microbe does not cause disease, but can if certain conditions are met
features of gram positive bacteria
- Outer peptidoglycan layer
- stains purple
features of gram negative bacteria
- out lipopolysaccharide layer
- porins provide channels through LPS
- stains pink
antibiotics that are from manmade sources
sulfa drugs
fluoroquinolones
linezolid
bacteriocidal
kills bacteria (technically all antibiotics are bacteriocidal at high doses)
bacteriostatic
inhibits growth of bacteria
sugar with the peptide attached for cross linking in peptidoglycan
NAM
amino acids needed to form cross-link
- D-Ala D-Ala on NAM
- pentaglycine chains linking the NAMs
steps of forming peptidoglycan cross-link
in cytoplasm
- synthesize NAM
- attach NAG and prenyl
- add peptide side chain
- flipping into periplasm
in periplasm
5. form crosslink
enzyme that makes crosslinks
transpeptidase
what facilitates transport of NAG and NAM into periplasm
bactoprenol
how does transpeptidation take place?
- penicillin binding protein has an active Ser that attacks the non-terminal D-Ala forming an ester bond
- Ester bond can be attacked by an amine in the pentaglycine chain via transpeptidation, forming a cross link
beta-lactam MoA
mimic D-Ala D-Ala to form a bond with PBP and prevent it from being used to make cross links, thus opening the cells wall
definition of a lactam ring
an intramolecular ring with an amine and a carboxylic acid linked with varying amounts of carbons (alpha=1, beta=2, and so on)
what part of beta-lactams mimics the D-Ala D-Ala peptide
the acidic withdrawing group on the lactam ring
Problems with beta lactams
- degraded by water and stomach acid due to its instability
- resistance via beta-lactamase, penicillinase, and other mechanisms
beta-lactamase function
hydrolysis of penicillins
location of beta-lactamase in gram positive bacteria
outside the peptidoglycan
location of beta-lactamase in gram negative bacteria
periplasmic space, between LPS and cytoplasmic membraine
general SAR of penicillins
- required S in ring
- ring system
- no substitution on ring
- “west end” has amide linkage
- aromatic or cyclic function in “west end” R group
- dimethyl on east end
penicillin G features
- early penicillin
- very Gm+ (no staph)
- little Gm-
- unstable when given orally
penicillin V features
- early penicillin
- very Gm+ (no staph)
- little Gm-
- given orally b/c of ether electron withdrawing group
early penicillins
Pen G
Pen V