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| Question | Answer |
| What did Ehrlich discover about altering structure of compounds? | Related compounds may have curative action increase independent of toxicity |
| What are the two types of effect antibiotics can have? | Bactericidal= kills bacteria bacteriostatic= stops growth |
| what are the 4 main sites of antibiotic action | -metabolism (antimetabolites) -cell wall synthesis -protein synthesis -nucleic acid synthesis |
| what was the first sulphonamide antibacterial |
Image:
prontosil (image/jpg)
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| what is prontosil structure |
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prontosil (image/jpg)
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| What are the functional groups of a sulphonamide | -amino terminus (cannot be changed or modified) -benzene ring (more active than other aromatics) -sulphonamide terminus (can be modified- swap hydrogens for other groups) |
| what molecule are sulphonamides similar to? what is this similarity called? | pAB (para-amino benzoic acid) isosterism |
| what is pAB used for | folate synthesis |
| how do sulphonamides work | incorporated instead of pAB, creates a false product, prevents folate synthesis |
| why does incorporation of a sulphonamide prevent folate synthesis | -next step after pAB is glutamate addition -glutamate can't be added to sulphonamide group |
| what is folic acid used for | 'one-carbon metabolism'- transfer of methyl groups (e.g. dUMP-->dTMP) |
| why are sulphonamides selectively toxic to bacteria? | Humans do not synthesise folate, sulphonamides block a pathway that is present in bacteria but not humans |
| what is the sulphonamide general structure | |
| why do sulphonamides work so well? | -they generate a false product- prevents a build up before the block (competition=overcome block) -bacteria have no uptake mechanisms for end-product -we don't synthesise folate- pAB not present in our cells |
| what blocks the action of sulphonamides | end products of folate metabolism (serine, thymine etc) |
| what effect do sulphonamides have on bacteria | usually bacteriostatic (become bacteriocidal in absence of thymine- 'thymineless death') |
| how is sulphonamide resistance achieved | -inc pAB levels -inc folate uptake -reduced uptake of drug -metabolism of drug |
| what are sulphonamides used for | UTIs, meningitis, and in veterinary medicine |
| what types of bacteria do sulphonamides affect | broad spectrum- Gram -ve and +ve |
| what are 2 related drugs that act by the same mechanism | -dapsone (used in combi therapy for leprosy) -p-amino salicyclic acid (tuberculosis) |
| what are some other drugs which target folate synthesis | dihydrofolate reductase inhibitors (enzyme also present in humans so toxic): -methotrexate (anticancer) -trimethoprim - selective for bacterial enzyme (bacterial IC50=0.01µM, mammalian IC50=300µM) |
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