Chapter 9 - Growth + Control of Microorgs

Question 1

T/F: Chemotherapeutic agents have selective toxicity.

Answer 1

TRUE: kill/inhibit microb path w/ little damage to host

Question 2

List 3 derivatives of chem. mod. natural antibiotics.

Answer 2

penicillin G/V are natural, ampicillin/amoxycillin semisynthetic, sulfonamides/trimethoprim synthetic

Question 3

“therapeutic index”?

Answer 3

Ratio of toxic dose/therapeutic dose (higher = safer)

Question 4

T/F: A larger toxicity index means a larger therapeutic dose.

Answer 4

FALSE

Question 5

T/F: The more selective the antimicrobial drug, the lower the therapeutic index.

Answer 5

FALSE

Question 6

T/F: The more selective the antimicrobial drug, the lower the therapeutic index.

Answer 6

FALSE: high selectivity = high therapeutic index (targets harmful more than host cell)

Question 7

List types of antimicrobial drugs in order of decreasing selectivity.

Answer 7

• 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)

Question 8

List two examples of cell wall synth. inhibitors

Answer 8

• Penicillin
• Ampicillin

Question 9

List two examples of prot. synth. inhibitors

Answer 9

• streptomycin
• chloramphenicol

Question 10

List an example of an antimetabolite

Answer 10

Sulfonamide(s)

Question 11

Most bact. cell wall inhibitors are ________________ derivatives and differ in side chain attached to __________ group.

Answer 11

Most bact. cell wall inhibitors are 6-AMINOPENICILLANIC ACID derivatives and differ in side chain attached to AMINO group.

Question 12

Describe mechanism by which bact. cell wall inhibitors function.

Answer 12

• 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

Question 13

Derivatives of penicillin will have a __________ and diff ___________ groups.

Answer 13

Derivatives of penicillin will have a BETA-LACTAM RING and diff SUBSTITUENT groups.

Question 14

T/F: Penicillins are bacteriostatic.

Answer 14

FALSE: They are bacteriocidal (attacks periplasmic space of G-, activates autolytic enz = holins)

Question 15

T/F: Protein synth inhibs are more effective against G- cells

Answer 15

TRUE

Question 16

T/F: Protein synthesis inhibs can only bind to small 30S ribosomes, but larger ribosomes (50S) are too large for these antibiotics to bond.

Answer 16

FALSE: Can bond to both

Question 17

Describe mechanism by which prot. synth. inhibs. function

Answer 17

• 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)

Question 18

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.

Answer 18

TRUE (Cyclohexanes are all connected through ether bond)`

Question 19

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.

Answer 19

TRUE (Cyclohexanes are all connected through ether bond)

Question 20

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).

Answer 20

TRUE

Question 21

____________ binds to 23S rRNA on 50S ribosomal subunits, inhibiting peptidyl transferase reaction and preventing __________ __________.

Answer 21

CHLORAMPHENICOL binds to 23S rRNA on 50S ribosomal subunits, inhibiting peptidyl transferase reaction and preventing PEPTIDE ELONGATION.

Question 22

T/F: Chloramphenical is toxic with numerous side effects and only used in life-threatening situations.

Answer 22

TRUE

Question 23

Describe the 4 steps to antibiotic resistance.

Answer 23

1. Lots of germs w/ few drug resistant
2. Antibiotics kill bact. causing illness + good bact. protecting body
3. Drug-resistant now allowed to grow
4. Some bact give drug-resistance to other bact

Question 24

List three mechanisms of drug resistance.

Answer 24

• 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

Question 25

What are the two sources of resistance genes in bacterial cells?

Answer 25

• bact chromosomes (results in rare spontaneous mutations)
• resistance plasmids transferred to other cells by conj, transduct, transform

Question 26

T/F: Transformation = direct physical contact of cells to transfer DNA, conjugation = transfer of free DNA from dead cell

Answer 26

FALSE: definitions are switched