Chapter 9 Flashcards
to stand still means?
stasis and static
prevent the growth of bacteria
bacteristatic
if a word has -Cidal it means?
to kill
permanent termination of an organisms vital process is?
Death
permentant loss of reproductive capability even under optimum growth conditions is?
the accepted microbiological definition of death
factors affecting the death rate are?
-the number of microbes
(the higher the number of microbes takes longer)
-the nature of the microorganisms in the population
-temperature
-acidity and alkalinity
-concentration
-presence of solvents, interfering organic matter and inhibitors.
Cold temperatures tend to?
preserve microbes.
Chemical reactions occur faster at?
warmer temperatures.
extremes in acidity or alkalinity enhance?
the killing of microbes.
the concentration is important in?
killing microbes
mode of action is?
how does it work
What are the cellular targets of physical and chemical agents?
cell wall
cell membrane
cellular synthetic process
proteins
Saliva, blood, and feces can inhibit the action of?
disinfectants and even the action of heat
Elevated temperature are?
microbicidal
lower temperatures are?
microbistatic
moist heat is?
hot water, boiling water, steam
dry heat is?
hot air, open flame
What operates at lower temperatures and shorter exposure times to achieve the same effectiveness as dry heat?
moist heat
Examples of moist heat?
boiling, pasteurization, steam under pressure
Pasteurization kills?
most of the microbes.
Steam under pressure ?
sterilizes
- What dehydrates the cell removing water necessary for metabolic reactions?
- Denatures proteins
- Requires a higher temperature and longer time than moist heat
dry heat
What are the two types of dry heat?
hot air oven
incineration
very high temperatures, oxidizes cells burning them to ashes is?
incineration
What is the principal effect of cold treatment to a microbe?
to slow the growth
What slows the growth of most microbes?
refrigeration
What stops the growth of most microbes?
freezing.
does cold kill microbes?
no
Temperatures for -70c to -135c can?
preserve cultures of bacteria, viruses, and fungi for long periods.
desiccation means?
dehydration
Can some microbes be killed by desiccation, but most is just stops growth?
yes
What is used to preserve food?
desiccation
Lyophilization is?
freeze drying.
Pure cultures are?
frozen instantaneously. and exposed to a vacuum that removes water
Freeze drying is a combination of?
freezing and dry
Lyophilization is?
static
desiccation is?
stasis
What is energy that is emitted from atomic activities and disperse at high velocity through matter or space?
Radiation
Ionizing radiation?
penetrates through things.
Gamma rays are the?
highest type of radiation.
is ionizing radiation sterile?
yes
is Ionizing radiation heat free?
yes
What can you use ionizing radiation for?
food and plastic things.
Non-ionizing radiation does not?
penetrate
Non-ionizing radiation does ______ but is more used for _______.
sterilize, disinfection
UV light is?
non-ionizing radiation
UV light kills cells by
affecting thymine dimer
Filtration is a way to?
removes microbes from air and liquids.
This process is?
Fluid or air is strained through a filter with openings large enough for the fluid to pass, but too small for microbes.
Filtration
Filtration is used for liquids that?
cannot withstand heat.
Filtration can be used in
water purification
High efficiency particulate air (HEPA) filters are used in hospital rooms and sterile rooms. This is a way of?
filtration
- Adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria, causing plasmolysis.
- Used in food preservation
Osmotic pressure
What is never a sterilizing technique?
osmotic pressure
Chemical agents in microbial control occur in?
liquids, gaseous, or solid state.
Chemicals dissolved in pure water as the convent is?
aqueous solutions
chemicals dissolved in pure alcohol is?
tinctures
What are something for ideal antimicrobial agent?
- rapid action
- solubility in water or alcohol
- long term stability
- broad spectrum action without being toxic to human and animal tissues.
- penetration of inanimate surfaces
- resistance to becoming inactivated by organic matter
- noncorrosive or non staining properties
- sanitizing and deodorizing
- affordability and ready available
- no antimicrobial reaches all these requirements
What are factors affecting the germicidal activity of chemicals?
- nature or the microorganisms
- nature of the material
- degree of contamination
- time of exposure
- strength and chemical action
- length of exposure
- composition of material being treated
Length of exposure is?
adequate contact time to act of microbes
What kind of objects are more reliably disinfected than those with pores or pockets?
smooth, solid objects
Chemicals used in food preservation are?
-acidic pH (vinegar) pickling food
What are active against gram-positive bacteria and fungi?
dyes
What is very low or very high pH can destroy or inhibit microbial cells?
- Ammonium hydroxide
- organic acids in food preservation
Acids and alkalis
