Dugga 3 Antibiotics Flashcards
What are the five main targets if antibacterial agents?
Cell metabolism, the cell wall, the plasma membrane, protein synthesis, nucleic acid function
What do sulphonamides require to function?
Primary aromatic amine group and a secondary sulphonamide group for good activity
What is a common metabolic reaction of sulphonamides?
N-acetylation
What are sulphonamides used for?
Treating infections of urinary tract, gastrointestinal tract and mucous membranes. Also in eye lotion
Which structure is sulphonamides similar to?
PABA para amino benzoic acid which is necessary for bacteria to bind to an enzyme to synthesise dihydroteroate. They act as a competitive inhibitor
What are sulphonamides an example of? (Which class of antibiotic is it?)
Antimetabolite, antibacterial agent that act against cell metabolism
Give 3 examples of antimetabolites
Sulphonamides, trimethoprim, sulphones
Give examples of antibacterial agents that inhibit cell wall synthesis
Penicillin
What is the structure of penicillin? How does it react?
Bicycling with a beta lactam ring fused to a thiazolidone ring. The beta lactam ring reacts irreversibly with the transpeptidase enzyme that cross links the bacterial cell wall.
How can penicillin be made more resistant to acid conditions?
By incorporating an electron withdrawing group into the acyl side chain
How can penicillin be protected from beta lactamase enzymes?
By adding steric shields
What structure gives the penicillin broad spectrum activity?
The alpha hydrophilic group on the acyl side chain
What are prodrugs of penicillin useful for? Which structures are used?
Masking polar groups to imported the absorption from GI tract. Extended esters are used
What groups does penicillin contain?
A highly unstable bicyclic system of a strained four membered beta lactam ring fused to a five membered thiazolidine ring
What amino acids does the skeleton structure of penicillin suggest to be derived from?
Cysteine and valine
Benzylpenicillin (Penicillin G) cannot be taken orally, why?
It is broken down by stomach acids and must be injected
Benzylpenicillin is ineffective against which types of bacteria?
Gram negative and those that produce beta lactamase
What does penicillin target?
The enzyme transpeptidase, responsible for interlinking during cell wall synthesis
What is the bacteria cell wall made up of?
Peptidoglycan structure made up of NAM and NAG
Penicillin has a conformation similar to the transition state conformation of what moiety during crosslinking?
D-Ala-D-Ala
Do bacteria have both D and L amino acids?
Bacteria have racemase that can convert L amino acids into D amino acids
What is the most important way bacteria gain resistance to penicillin?
Beta lactamase enzymes
Most if not all Gram negative bacteria produce what that makes them more resistant to penicilin?
Beta lactamase enzymes
What was originally the only way to prepare different penicillins?
By varying fermentation conditions
