BME 245L Final Exam Questions &
Answers (Grade A+)
Steam sterilization (autoclave) -
correct answer ✅Usually 30 minutes at 121 degrees C; Most
widely used and most dependable; Heat compatible:
OK - polypropylene,silicone, metals
Not OK - polystyrene, polyethylenes
polypropylene -
correct answer ✅conical tubes, microcentrifuge tubes,
micropipette tips
polystyrene -
correct answer ✅all of our tissue culture flasks, well plates,
serological pipettes; cell culture: treat w/plasma = less hydrophobic,
fibronectin adsorb/cells attach
Ethylene oxide (gas phase sterilization) -
correct answer ✅sterilizing items sensitive to heat;
Residue harmful, aeration to remove residue.
Ionizing radiation (gamma radiation) -
correct answer ✅Provides good penetration, but sometimes
damage surfaces of materials; High cost/not used in health care
,BME 245L Final Exam Questions &
Answers (Grade A+)
facilities; Large scale production (all the conical tubes and flasks,
including T75 for tissue culture)
Peracetic acid
Liquid -
correct answer ✅Sterilize equipment with narrow long lumens;
endoscopes
Dry heat (oven) -
correct answer ✅autoclave no steam;
Much higher temperatures, longer time; powders if they are not
susceptible to heat
Filter sterilization -
correct answer ✅Physically remove particles. ex:
0.22 um pore filter
Useful for heat sensitive liquids
Ultraviolet light -
correct answer ✅Directional:cannot sterilize surfaces that aren't
illuminated.
,BME 245L Final Exam Questions &
Answers (Grade A+)
Poor penetration - UV light does not go through much
Not FDA approved
Lab disinfectants -
correct answer ✅70% Ethanol (more effective than 100%), 10%
Sodium hypochloride (bleach) for mammalian cells; eventually goes
bad from light and heat. bad ~ week
Other disinfectants -
correct answer ✅Hydrogen peroxide (3%), Iodine, Phenol, Lysol
(quarternary ammonium compounds)
Disinfection vs. Sterilization -
correct answer ✅•* Disinfection *= Destroying PATHOGENIC
microbes except for spores (ie chemical disinfection, pasteurization)
•* Sterilization *= Killing ALL microbes (good & bad) (ie autoclave,
flash sterilization, low temp sterilization)
in lab words: disinfection is less effective sterilization. Keep the
outside of things clean
, BME 245L Final Exam Questions &
Answers (Grade A+)
We sterilize our hands with 70% ethanol before touching anything
inside the biological safety cabinet. -
correct answer ✅False! Disinfect!
Mycoplasma -
correct answer ✅Preventing mycoplasma contamination is
difficult. For one, mycoplasma cells are small (0.3-0.8 µM in
diameter) and pleomorphic (8), allowing them to pass through
standard filtration membranes. Secondly, mycoplasmas lack cell
walls. This makes them impervious to cell culture antibiotics that
inhibit cell wall synthesis, such as penicillin. Effective antibiotics do
exist, however, their continuous use in cell culture is not
recommended due to possible cytotoxicity. Third, mycoplasmas are
able to reach high concentrations in the media of infected cells
without noticeable turbidity (9). This makes detection via visual
inspection difficult. Lastly, while the primary source of mycoplasma
contamination is likely other cell cultures, mycoplasmas from lab
personnel are a potential source as well (7). Hence, the only reliable
ways to minimize contamination are to test routinely (and
frequently), practice safe cell culture techniques and to obtain cells
from reputable sources such as the American Type Culture
Collection (ATCC).
Answers (Grade A+)
Steam sterilization (autoclave) -
correct answer ✅Usually 30 minutes at 121 degrees C; Most
widely used and most dependable; Heat compatible:
OK - polypropylene,silicone, metals
Not OK - polystyrene, polyethylenes
polypropylene -
correct answer ✅conical tubes, microcentrifuge tubes,
micropipette tips
polystyrene -
correct answer ✅all of our tissue culture flasks, well plates,
serological pipettes; cell culture: treat w/plasma = less hydrophobic,
fibronectin adsorb/cells attach
Ethylene oxide (gas phase sterilization) -
correct answer ✅sterilizing items sensitive to heat;
Residue harmful, aeration to remove residue.
Ionizing radiation (gamma radiation) -
correct answer ✅Provides good penetration, but sometimes
damage surfaces of materials; High cost/not used in health care
,BME 245L Final Exam Questions &
Answers (Grade A+)
facilities; Large scale production (all the conical tubes and flasks,
including T75 for tissue culture)
Peracetic acid
Liquid -
correct answer ✅Sterilize equipment with narrow long lumens;
endoscopes
Dry heat (oven) -
correct answer ✅autoclave no steam;
Much higher temperatures, longer time; powders if they are not
susceptible to heat
Filter sterilization -
correct answer ✅Physically remove particles. ex:
0.22 um pore filter
Useful for heat sensitive liquids
Ultraviolet light -
correct answer ✅Directional:cannot sterilize surfaces that aren't
illuminated.
,BME 245L Final Exam Questions &
Answers (Grade A+)
Poor penetration - UV light does not go through much
Not FDA approved
Lab disinfectants -
correct answer ✅70% Ethanol (more effective than 100%), 10%
Sodium hypochloride (bleach) for mammalian cells; eventually goes
bad from light and heat. bad ~ week
Other disinfectants -
correct answer ✅Hydrogen peroxide (3%), Iodine, Phenol, Lysol
(quarternary ammonium compounds)
Disinfection vs. Sterilization -
correct answer ✅•* Disinfection *= Destroying PATHOGENIC
microbes except for spores (ie chemical disinfection, pasteurization)
•* Sterilization *= Killing ALL microbes (good & bad) (ie autoclave,
flash sterilization, low temp sterilization)
in lab words: disinfection is less effective sterilization. Keep the
outside of things clean
, BME 245L Final Exam Questions &
Answers (Grade A+)
We sterilize our hands with 70% ethanol before touching anything
inside the biological safety cabinet. -
correct answer ✅False! Disinfect!
Mycoplasma -
correct answer ✅Preventing mycoplasma contamination is
difficult. For one, mycoplasma cells are small (0.3-0.8 µM in
diameter) and pleomorphic (8), allowing them to pass through
standard filtration membranes. Secondly, mycoplasmas lack cell
walls. This makes them impervious to cell culture antibiotics that
inhibit cell wall synthesis, such as penicillin. Effective antibiotics do
exist, however, their continuous use in cell culture is not
recommended due to possible cytotoxicity. Third, mycoplasmas are
able to reach high concentrations in the media of infected cells
without noticeable turbidity (9). This makes detection via visual
inspection difficult. Lastly, while the primary source of mycoplasma
contamination is likely other cell cultures, mycoplasmas from lab
personnel are a potential source as well (7). Hence, the only reliable
ways to minimize contamination are to test routinely (and
frequently), practice safe cell culture techniques and to obtain cells
from reputable sources such as the American Type Culture
Collection (ATCC).
