Chapter 9 - Growth + Control of Microorgs Flashcards
T/F: Chemotherapeutic agents have selective toxicity.
TRUE: kill/inhibit microb path w/ little damage to host
List 3 derivatives of chem. mod. natural antibiotics.
penicillin G/V are natural, ampicillin/amoxycillin semisynthetic, sulfonamides/trimethoprim synthetic
“therapeutic index”?
Ratio of toxic dose/therapeutic dose (higher = safer)
T/F: A larger toxicity index means a larger therapeutic dose.
FALSE
T/F: The more selective the antimicrobial drug, the lower the therapeutic index.
FALSE
T/F: The more selective the antimicrobial drug, the lower the therapeutic index.
FALSE: high selectivity = high therapeutic index (targets harmful more than host cell)
List types of antimicrobial drugs in order of decreasing selectivity.
- inhib. of bact. cell wall synth. (does not targ euk)
- protein synth. inhib. (discrim. betw. bact ribos and euk ribos)
- metabolic antagonists (block metabol pathway)
- nucleic acid synth inhib. (not as many diff betw bact and euk nuc acid synth)
List two examples of cell wall synth. inhibitors
- Penicillin
- Ampicillin
List two examples of prot. synth. inhibitors
- streptomycin
- chloramphenicol
List an example of an antimetabolite
Sulfonamide(s)
Most bact. cell wall inhibitors are ________________ derivatives and differ in side chain attached to __________ group.
Most bact. cell wall inhibitors are 6-AMINOPENICILLANIC ACID derivatives and differ in side chain attached to AMINO group.
Describe mechanism by which bact. cell wall inhibitors function.
- thought to inhib. last step (transpeptidation) in synth
- penicillin = analogue to a peptide in peptidoglycan
- prevents X-linkage of peptidoglycan (osmotic lysis of cell)
- act on growing bact that synth new peptidoglycan
- may also stimulate prot which form holes in plasma memb
Derivatives of penicillin will have a __________ and diff ___________ groups.
Derivatives of penicillin will have a BETA-LACTAM RING and diff SUBSTITUENT groups.
T/F: Penicillins are bacteriostatic.
FALSE: They are bacteriocidal (attacks periplasmic space of G-, activates autolytic enz = holins)
T/F: Protein synth inhibs are more effective against G- cells
TRUE
T/F: Protein synthesis inhibs can only bind to small 30S ribosomes, but larger ribosomes (50S) are too large for these antibiotics to bond.
FALSE: Can bond to both
Describe mechanism by which prot. synth. inhibs. function
- mistranslated prot inserted into plas memb, activates stress response which releases hydroxyl radicals (death)
- inhibit step in protein synth (aminoacyl-tRNA binding, peptide bond form, mRNA reading, translocation)
T/F: Gentamicin C, a prot. synth inhibitor, contains three cyclohexane rings arranged in a loop whereas streptomycin’s three cyclohexane rings are arranged in a straight line.
TRUE (Cyclohexanes are all connected through ether bond)`
T/F: Gentamicin C, a prot. synth inhibitor, contains three cyclohexane rings arranged in a loop whereas streptomycin’s three cyclohexane rings are arranged in a straight line.
TRUE (Cyclohexanes are all connected through ether bond)
T/F: It is not known whether streptomycin is bacteriocidal cuz mechanism by which it attacks the cell causes the cell to remain intact (can’t differentiate between dead/live cells if cultured).
TRUE
____________ binds to 23S rRNA on 50S ribosomal subunits, inhibiting peptidyl transferase reaction and preventing __________ __________.
CHLORAMPHENICOL binds to 23S rRNA on 50S ribosomal subunits, inhibiting peptidyl transferase reaction and preventing PEPTIDE ELONGATION.
T/F: Chloramphenical is toxic with numerous side effects and only used in life-threatening situations.
TRUE
Describe the 4 steps to antibiotic resistance.
- Lots of germs w/ few drug resistant
- Antibiotics kill bact. causing illness + good bact. protecting body
- Drug-resistant now allowed to grow
- Some bact give drug-resistance to other bact
List three mechanisms of drug resistance.
- Alteration of target enz/organelle (penicillin)
- inactiv of drug by degredation (often in plasmids, great in biofilms)
- inactiv of drug by modification (chloramphenicol)
- pump drug out (antiporters)
- prevent entry into cell (can’t bind or penetrate pathogen, bacterial decr in permeability)
- use alt pathways/increase prod of target metabolite
What are the two sources of resistance genes in bacterial cells?
- bact chromosomes (results in rare spontaneous mutations)
- resistance plasmids transferred to other cells by conj, transduct, transform
T/F: Transformation = direct physical contact of cells to transfer DNA, conjugation = transfer of free DNA from dead cell
FALSE: definitions are switched
