BIOL 2051 LSU LAB FINAL EXAM 2025
QUESTIONS AND ANSWERS
Antibiosis - ANS a symbiotic relationship between two organisms in which there is inhibition,
injury, or killing of one organism by another
what does penicillin interfere with and what type of bacteria is it most effective against? -
ANS cell wall synthesis; Gram positive due to the thick peptidoglycan layer
antimicrobial agents - ANS kill or inhibit the growth of microorganisms
cidal agents - ANS lethal to microorganisms
lytic agents - ANS a type of cidal agent that lyses or breaks open cells
static agents - ANS only inhibit the growth of microorganisms
T/F: If a static agent is removed, the microorganism will continue to grow. - ANS true
disinfectants - ANS antimicrobial agents for use on inanimate surfaces
examples of disinfectants - ANS ammonia, ethanol, bleach, vesphene
1 @COPYRIGHT THESTAR 2025/2026
,antiseptics - ANS antimicrobial agents that can be applied to skin but are not necessarily safe
for ingestion
examples of antiseptics - ANS ethanol and iodine
antibiotics - ANS antimicrobial chemotherapeutic agents of microbial origin used to kill or
inhibit the growth of bacteria - CAN BE TAKEN ORALLY OR THROUGH IV
examples of antibiotics - ANS penicillin and streptomycin
Penicillin G is rarely used today due to what? - ANS widespread antibiotic resistance
susceptible or sensitive - ANS bacteria will not grow
what to look for when looking for sensitivity in a bacteria - ANS zone of inhibition
mode of action - ANS the way the agent kills or inhibits growth
mode of action for erythromycin and chloramphenicol - ANS inhibits protein synthesis by
targeting the 50S subunit of the ribosome
Which antibiotic can affect the 50S subunit of the ribosome in bacteria along with the 70S
subunit in humans? - ANS chloramphenicol
mode of action for gentamicin, tetracycline, and streptomycin - ANS inhibits protein
synthesis by targeting the 30S subunit of the ribosome
streptomycin is only effective against: - ANS Gram positive and Gram negative bacteria that
don't have a resistance mechanism against the antibiotic
2 @COPYRIGHT THESTAR 2025/2026
, Kirby-Bauer method - ANS disc diffusion method in which different antimicrobial agents are
test where filter paper discs are saturated with agents that, over time, will diffuse into the
medium
zone of inhibition - ANS clear area in which there is no bacterial growth
mechanisms of antibiotic resistance - ANS 1. activate drug efflux pumps to push antibiotic
out of system
2. make enzymes to change or modify antibiotic
3. make enzymes to inactivate antibiotic
4. modify cell wall to keep antibiotic from entering
mode of action for cefoxitin and ampicillin - ANS beta-lactams (like penicillin) - inhibits cell
wall synthesis
how to measure zone of inhibition - ANS due to overlapping zones, measure radius center
until edge; multiply radius by 2 to get the diameter
FINAL ANSWER: the diameter in mm !!!
(ruler will be cm so multiply answer by 10 - move decimal point one place to the right)
Pseudomonas fluorescens - ANS Gram negative
Resistant to chlorox (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to lysol, listerene, ethanol, H2O2, vesphene
Staphylococcus epidermidis (exp. 8) - ANS Gram positive
Resistant to vesphene (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to H2O2, listerene, chlorox, ethanol, lysol
3 @COPYRIGHT THESTAR 2025/2026
QUESTIONS AND ANSWERS
Antibiosis - ANS a symbiotic relationship between two organisms in which there is inhibition,
injury, or killing of one organism by another
what does penicillin interfere with and what type of bacteria is it most effective against? -
ANS cell wall synthesis; Gram positive due to the thick peptidoglycan layer
antimicrobial agents - ANS kill or inhibit the growth of microorganisms
cidal agents - ANS lethal to microorganisms
lytic agents - ANS a type of cidal agent that lyses or breaks open cells
static agents - ANS only inhibit the growth of microorganisms
T/F: If a static agent is removed, the microorganism will continue to grow. - ANS true
disinfectants - ANS antimicrobial agents for use on inanimate surfaces
examples of disinfectants - ANS ammonia, ethanol, bleach, vesphene
1 @COPYRIGHT THESTAR 2025/2026
,antiseptics - ANS antimicrobial agents that can be applied to skin but are not necessarily safe
for ingestion
examples of antiseptics - ANS ethanol and iodine
antibiotics - ANS antimicrobial chemotherapeutic agents of microbial origin used to kill or
inhibit the growth of bacteria - CAN BE TAKEN ORALLY OR THROUGH IV
examples of antibiotics - ANS penicillin and streptomycin
Penicillin G is rarely used today due to what? - ANS widespread antibiotic resistance
susceptible or sensitive - ANS bacteria will not grow
what to look for when looking for sensitivity in a bacteria - ANS zone of inhibition
mode of action - ANS the way the agent kills or inhibits growth
mode of action for erythromycin and chloramphenicol - ANS inhibits protein synthesis by
targeting the 50S subunit of the ribosome
Which antibiotic can affect the 50S subunit of the ribosome in bacteria along with the 70S
subunit in humans? - ANS chloramphenicol
mode of action for gentamicin, tetracycline, and streptomycin - ANS inhibits protein
synthesis by targeting the 30S subunit of the ribosome
streptomycin is only effective against: - ANS Gram positive and Gram negative bacteria that
don't have a resistance mechanism against the antibiotic
2 @COPYRIGHT THESTAR 2025/2026
, Kirby-Bauer method - ANS disc diffusion method in which different antimicrobial agents are
test where filter paper discs are saturated with agents that, over time, will diffuse into the
medium
zone of inhibition - ANS clear area in which there is no bacterial growth
mechanisms of antibiotic resistance - ANS 1. activate drug efflux pumps to push antibiotic
out of system
2. make enzymes to change or modify antibiotic
3. make enzymes to inactivate antibiotic
4. modify cell wall to keep antibiotic from entering
mode of action for cefoxitin and ampicillin - ANS beta-lactams (like penicillin) - inhibits cell
wall synthesis
how to measure zone of inhibition - ANS due to overlapping zones, measure radius center
until edge; multiply radius by 2 to get the diameter
FINAL ANSWER: the diameter in mm !!!
(ruler will be cm so multiply answer by 10 - move decimal point one place to the right)
Pseudomonas fluorescens - ANS Gram negative
Resistant to chlorox (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to lysol, listerene, ethanol, H2O2, vesphene
Staphylococcus epidermidis (exp. 8) - ANS Gram positive
Resistant to vesphene (could be due to any of the 4 mechanisms of antibiotic resistance)
Sensitive to H2O2, listerene, chlorox, ethanol, lysol
3 @COPYRIGHT THESTAR 2025/2026
