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1.1 The study of life Read Online
Viewed from space, Earth offers no clues about the diversity of life forms that reside there. The first forms of life on Earth are thought to have been microorganisms that existed for billions of years in the ocean before plants and animals appeared. The mammals, birds, and flowers so familiar to us are all relatively recent, originating 130 to 200 million years ago. Humans have inhabited this planet for only the last 2.5 million years, and only in the last 200,000 years have humans started looking like we do today.
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Question: Which of the following is not a sterilization method?
Choices:
hot air oven
autoclave
pasteurization
filtration
Question: Nosocomial infections
Choices:
are acquired at various social events.
are acquired while in the hospital.
occur because of a susceptible population and presence of disease causing organisms.
are acquired at sporting events.
are acquired while in the hospital AND occur because of a susceptible population and presence of disease causing organisms.
Question: Phenolics
Choices:
denature proteins and destroy cytoplasmic membranes.
remain effective in the presence of detergents or organic material.
such as triclosan, have been used widely in various lotions and soaps.
reliably inactivate all groups of viruses.
denature proteins and destroy cytoplasmic membranes, remain effective in the presence of detergents or organic material, AND phenolics such as triclosan, have been used widely in various lotions and soaps.
Question: A common application of dry heat in the microbiology laboratory is to
Choices:
prepare specimens for study.
sterilize media.
sterilize plastics.
sterilize the inoculating loop.
Question: Generally, membrane filters are not used to remove
Choices:
bacteria from liquids.
microorganisms from gases.
spoilage agents from alcoholic beverages.
enzymes.
Question: Hexachlorophene has been particularly effective against
Choices:
Staphylococcus aureus.
Micrococcus aureus.
Escherichia coli.
Enterobacter aerogenes.
Question: Chemical germicides
Choices:
may react irreversibly with proteins/enzymes.
may react with cytoplasmic membranes or viral envelopes.
may be disinfecting or even sterilizing.
are sensitive to dilution factor, time of contact, and temperature of use.
All of the choices are true.
Question: To reduce or eliminate disease/spoilage causing organisms, food is often subjected to
Choices:
heat.
chemical additives.
radiation.
cold.
All of the choices are correct.
Question: Pasteurization
Choices:
is the use of heat to sterilize food products.
is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level.
is a process which uses intense cold to kill microorganisms on foods.
is a process which uses short bursts of radiation to kill microorganisms on foods.
Question: Typical conditions used for sterilization are
Choices:
121°C at 15 psi for 15 minutes.
80°C for 15 minutes.
100°C for 10 minutes.
72°C for 15 seconds.
Question: Gamma irradiation
Choices:
has not been approved for use on food.
can be used to either sterilize or pasteurize, depending on the dose of radiation.
leaves some radioactive particles in the treated substance.
usually kills by disrupting cell membranes.
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