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Chapter21 Question and answers 100% correct

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Chapter21 Question and answers 100% correct Chapter 6-Microbiology What are the physical requirements for microbial growth? - correct answer Temperature, pH, and osmotic pressure Temperature - correct answer Most microorganisms grow well at the temperatures that humans favor; but there a...

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  • August 11, 2024
  • 17
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers

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  • chapter21 question and answers 100 correct

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  • Microbiology

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Chapter 6-Microbiology
What are the physical requirements for microbial growth? - correct answer
✔Temperature, pH, and osmotic pressure


Temperature - correct answer ✔Most microorganisms grow well at the
temperatures that humans favor; but there are three major ranges of
temperature: psychorophiles, meosphiles, thermophiles


psychorophiles - correct answer ✔cold-loving microbes (-10 to 20)


Mesophiles - correct answer ✔moderate-temperature loving microbes (10 to
50)


Thermophiles - correct answer ✔heat loving microbes (40 to 73)


Maximum growth temperature - correct answer ✔highest temperature at
which growth is possible


optimum growth temperature - correct answer ✔temperature at which the
species grows back


minimum growth temperature - correct answer ✔lowest temperature at which
the species will grow


Typically the max and min growth temperatures are only about 30 degrees
Celsius apart

,psychotrophs - correct answer ✔food microbiologists favor, this group is
known for spoilage of food


Why refrigerate? - correct answer ✔based on the principle that microbial
reproduction rates decrease at low temperatures (or entirely dormant)


hyperthermophiles or extreme thermophiles - correct answer ✔arcahe; have
an optimum growht temperature of 80* C or more; live in hot springs and
sulfur important in their metabolic activity


What pH do bacteria typically grow in? - correct answer ✔neutrality (between
6.5 adn 7.5)
Cutlured bacteria often produce acids that eventualy interfere with their own
growth; chemical buffers must be included in growth medium


acidophiles - correct answer ✔remarkably tolerant of acidity


How do most microorganisms obtain all their nutrients? - correct answer
✔through solution from their surrounding water; thus they require water for
growth;


How does high osmotic pressure effect bacteria? - correct answer ✔When
concentration of solutes is higher in the cell (hypertonic)


When concentration of solutes is higher outside the cell - correct answer
✔Cell will shrink, removes necessary water


Plasmolysis - correct answer ✔shrinkage of the cell cytoplasm

, Plasma membrane pulls away from the cell wall; addition of salts to a solution
will increase osmotic pressure (can be used for food preservation)


Extreme Halophiles - correct answer ✔adapted well to high salt
concentrations that they actually require them for growth


Obligate halophiles - correct answer ✔require salt for growth


Facultative halophiles - correct answer ✔do not require high salt
concentrations but are able to grow in salt concentrations up to 2%; few can
tolerate even up to 15%


Typical medium composed of? - correct answer ✔1.5% agar, the rest is
water!; if all water, the enviornment is hypotonic, water will move into the cell-
lyses


What are the chemical requirements of microbial growth? - correct answer
✔carbon, nitrogen, suflur, phosphorus, trace elements, oxygen, and organic
growth factors


Why carbon? - correct answer ✔one of the most important requirements for
microbial growth; carbon is the structural backbone of living matter; it is neeed
for all organic ompounds that make up a living cell; half of the dry weight of a
living cell is carbon


Chemoheterotrophs - correct answer ✔get most of their carbon from the
source of their energy


Nitrogen, sulfur, phosphorus - correct answer ✔DNA and RNA and ATP
synthesis: require nitrogen and phosphorous

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