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35 Cards in this Set
- Front
- Back
generation time |
time required for a cell to divide or a population of cells to double.
-it is most accurately calculated during the logarithmic growth phase |
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initial stationary phase |
a. adjustment of bacteria to the new environment b. few cells die due to osmotic shock |
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lag phase |
a. lag in reproduction or cell division b. cells are still viable and metabolically very active c. cells increase in size d. cells are getting ready to divide |
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logarithmic growth phase |
a. maximum metabolism b. maximum cell division c. cell size becomes normal d. shortest generation time found here e. staining becomes most effective here |
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maximum stationary phase |
a. number of cells dividing equals the number of cells dying b. growth rate slows down due to accumulation of wastes, depletion of nutrients and over crowding c. endospores and exospores |
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logarithmic death phase |
a. cells die at a constant rate, much faster than divisions b. few cells still survive, curve never reaches zero |
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sterilization |
process of destroying all forms of life, including spores and viruses, utilizing either physical or chemical agents
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disinfection |
process by which all vegetative cells are killed, but not spores unless prolonged contact (20 min) |
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disinfectant |
chemical substance used on non-living objects that is toxic to skin and mucous membranes, kills vegetative cells and viruses, but not spores unless prolonged contact
a. used on non living objects b. toxic to living tissue c. purpose- for disinfection of non-living tissue |
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antiseptic |
chemical substance that is not toxic to skin and mucous membranes, kills vegetative cells but not spores
a. used on living tissue b. non-toxic to living tissue c. purpose- for disinfection of living tissue |
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bactericidal |
a. inhibits growth and kills vegetative cells b. cide means killer |
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bacteriostatic |
a. inhibits growth but does not kill vegetative cells b. temporary suspension of bacterial activities |
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sterilization by heat |
involves denaturation of cell proteins and melting of membrane lipids |
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autoclave |
-121 degrees -15 lb./in^2 -15 minutes
use is limited in that you can not put heat sensitive materials and the pH of your material may be unintentionally reduced due to the acceleration of production of gases such as CO2 |
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boiling of material |
*not a true form of sterilization considered an emergency sterilization |
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tyndallization |
used to kill vegetative cells, moist steam at 100 C at atmospheric pressure for one hour on three days -advantage: heat sensitive material can be processed |
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dry heat |
160 C - 180 C for 1 1/2 hours - no moisture, no pressure |
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phenol |
Lister used it as an aerosol disinfectant to surgical instruments -melts lipids -destructs protein gates -inactivation of enzymes |
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chlorhexidine |
-denatures proteins |
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halogens |
strong oxidizing agents that remove H-bonds -denatures proteins (non functional) |
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alcohols |
swabbing skin, instruments -denatures proteins -melts lipids |
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heavy metals |
-high concentration of this = bactericidal effect -noncompetitive inhibition of enzymes |
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surfactants |
works to lower the surface tension of water and is often used in conjunction with other disinfectant to increase their effectiveness |
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quaternary ammonium compound |
cationic detergents a. enzyme inhibition b. protein denaturation c. disruption of cell membrane |
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oxidizing agents: hydrogen peroxide |
a good antiseptic for irrigation of open and shallow wounds because of its cleansing action and the release of oxygen due to the presence of cellular catalase |
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ethylene oxide |
denaturation of proteins in cell wall, cell membrane, enzymes a. kills all microbes and spores b. requires long exposure times 4-24 hours c. toxic 4. explosive in pure form 5. high penetrating ability 6. medical supplies, plastic ware, mattresses, textiles |
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millipore filter |
best way for heat sensitive materials a. most commonly used b. most effective c. electrostatic forces do play some role in filtration d. pore size: .45 microns, .22 microns .01 microns |
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hepa filter |
a. laminar flow hoods b. filtering exhaust systems like biohazard buildings |
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ultraviolet light |
260 nanometers causes most severe damage to the DNA molecule (bactericidal effect) -formation of thymine-thymine dimers
disadvantage: a. poor penetration power b. little effect on spores |
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photoreactivation |
90% effective photoreactivation enzyme a. recognize thymine thymine dimer b. breaks thymine thymine dimer c. restores normal DNA structure
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excision |
10% effective DNA polymerases and DNA ligases a. recognize T-T dimer b. excision and removal of T-T dimers c. repair damaged DNA by synthesis of new DNA to fill gap |
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ionizing radiation |
causes splitting or ionization of water molecules -formation of free radicals -denaturation of proteins and DNA |
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gamma rays |
have greatest penetration power -used in food and preservation of spices |
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pateurization |
controlled heating below boiling a. kills pathogens b. reduces total number of normal flora |
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4 sterilization of milk |
under vacuum, less than 5 seconds -74C---140C---74C -used for coffee creamers and areas of poor refrigeration |