BIO 201 EXAM 3 (MICROBIOLOGY) – Questions With
Verified Solutions
The term facultative refers to ________. Correct Ans - the ability to exist in
a wide range of conditions
A microorganism that does not have catalase or superoxide dismutase would
find it difficult to live in an environment with _____. Correct Ans - oxygen
A cell exposed to a hypertonic environment will _____ by osmosis. Correct
Ans - lose water
During binary fission, one bacterial cell becomes _______ cells.
a)four genetically identical
b)four genetically unique
c)two genetically identical
d)two genetically unique Correct Ans - two genetically identical
Binary fission involves one bacterial cell dividing into two genetically identical
cells.
What factors can affect the doubling time of a bacterial cell?
Temperature
Moisture
pH
Oxygen levels
All of these factors can affect growth rates. Correct Ans - All of these
factors can affect growth rates.
Temperature
Moisture
pH
Oxygen levels
There are many physical and chemical factors that can affect growth,
including temperature, oxygen and carbon dioxide levels, water activity,
pressure, pH, availability of nutrients, and several other factors.
,Pathogens usually have _____ doubling times. Correct Ans - short
Pathogens usually have short doubling times, allowing the population to grow
quickly before it is eliminated from the body.
You ingest 20 cells of Salmonella. This bacterium has a doubling time of 30
minutes. After 4 hours, how many of these bacteria would be present in the
body (assuming no immune system responses or other biological activities
affect its growth)? Correct Ans - 5,120
Four hours represents 8 generations (or 8 doubling times of 30 minutes each).
A starting population of 20 cells would become 5,120 after four hours. You can
use this equation to solve the problem: Nf = (Ni)2n.
A pathogen would most accurately be described as a ______. Correct Ans -
parasite
An organism that can synthesize all its required organic components from
CO2 using energy from the sun is a _______. Correct Ans - photoautotroph
How common are food spoilage microorganisms? Correct Ans - Almost
all of our foods contain them
The most common organisms causing food spoilage are bacteria, _______.
Correct Ans - yeasts, and molds
This animation shows that food spoilage microorganisms can be classified by
their ________. Correct Ans - growth temperature preferences
By keeping food cold, the growth of microorganisms is ________. Correct
Ans - minimized
In this animation, on which day does the room temperature orange begin to
show spoilage? Correct Ans - Day 8
Phase during which nutrient depletion and accumulation of wastes begin to
slow cell growth such that the rate of cell increase equals the rate of cell death
Correct Ans - stationary growth phase
, Phase during which cells are growing very quickly, at their maximum rate of
cell division Correct Ans - Exponential growth phase
Adjustment period during which cells are dividing slowly while they adjust to
growth conditions Correct Ans - Lag phase
Nutrient depletion and waste accumulation prevent cell growth and cells die
exponentially Correct Ans - Death phase
Phase and reasons Correct Ans - When cells are inoculated into fresh
media, they experience a lag phase during which they adjust to the new media
and during this time they grow very slowly. Once adjustments are made, the
cells begin to grow very rapidly, at their maximum growth rate. This period of
rapid growth is referred to as the exponential growth phase. The growing cells
begin to deplete nutrients and wastes begin to accumulate. This leads to
stationary growth phase, during which growth continues slowly but the
number of viable cells does not increase because any increase in cell number
due to growth is balanced by cell death. Finally when nutrients are sufficiently
depleted and enough wastes have accumulated, the culture enters the death
phase, during which cells die rapidly.
Review the many ways in which microbes process oxygen by completing each
sentence. Then, please arrange the sentences in a logical order Correct
Ans - With respect to oxygen requirements, an aerobe can use gaseous
oxygen and possesses enzymes to process toxic oxygen products.
1
Expanding on this classification, an obligate aerobe cannot grow without
oxygen.
2
Microaerophiles do not grow at normal atmospheric oxygen concentrations,
but they do require very minute concentrations of oxygen for metabolism.
3
Still other organisms, called facultative anaerobes, can grow with or without
oxygen, but grow faster when oxygen is present.
4
Anaerobes represent a final group of organisms, whose members lack the
required enzymes needed for using oxygen in respiration and may not be able
to tolerate any free oxygen in their environment (obligate anaerobes).
Verified Solutions
The term facultative refers to ________. Correct Ans - the ability to exist in
a wide range of conditions
A microorganism that does not have catalase or superoxide dismutase would
find it difficult to live in an environment with _____. Correct Ans - oxygen
A cell exposed to a hypertonic environment will _____ by osmosis. Correct
Ans - lose water
During binary fission, one bacterial cell becomes _______ cells.
a)four genetically identical
b)four genetically unique
c)two genetically identical
d)two genetically unique Correct Ans - two genetically identical
Binary fission involves one bacterial cell dividing into two genetically identical
cells.
What factors can affect the doubling time of a bacterial cell?
Temperature
Moisture
pH
Oxygen levels
All of these factors can affect growth rates. Correct Ans - All of these
factors can affect growth rates.
Temperature
Moisture
pH
Oxygen levels
There are many physical and chemical factors that can affect growth,
including temperature, oxygen and carbon dioxide levels, water activity,
pressure, pH, availability of nutrients, and several other factors.
,Pathogens usually have _____ doubling times. Correct Ans - short
Pathogens usually have short doubling times, allowing the population to grow
quickly before it is eliminated from the body.
You ingest 20 cells of Salmonella. This bacterium has a doubling time of 30
minutes. After 4 hours, how many of these bacteria would be present in the
body (assuming no immune system responses or other biological activities
affect its growth)? Correct Ans - 5,120
Four hours represents 8 generations (or 8 doubling times of 30 minutes each).
A starting population of 20 cells would become 5,120 after four hours. You can
use this equation to solve the problem: Nf = (Ni)2n.
A pathogen would most accurately be described as a ______. Correct Ans -
parasite
An organism that can synthesize all its required organic components from
CO2 using energy from the sun is a _______. Correct Ans - photoautotroph
How common are food spoilage microorganisms? Correct Ans - Almost
all of our foods contain them
The most common organisms causing food spoilage are bacteria, _______.
Correct Ans - yeasts, and molds
This animation shows that food spoilage microorganisms can be classified by
their ________. Correct Ans - growth temperature preferences
By keeping food cold, the growth of microorganisms is ________. Correct
Ans - minimized
In this animation, on which day does the room temperature orange begin to
show spoilage? Correct Ans - Day 8
Phase during which nutrient depletion and accumulation of wastes begin to
slow cell growth such that the rate of cell increase equals the rate of cell death
Correct Ans - stationary growth phase
, Phase during which cells are growing very quickly, at their maximum rate of
cell division Correct Ans - Exponential growth phase
Adjustment period during which cells are dividing slowly while they adjust to
growth conditions Correct Ans - Lag phase
Nutrient depletion and waste accumulation prevent cell growth and cells die
exponentially Correct Ans - Death phase
Phase and reasons Correct Ans - When cells are inoculated into fresh
media, they experience a lag phase during which they adjust to the new media
and during this time they grow very slowly. Once adjustments are made, the
cells begin to grow very rapidly, at their maximum growth rate. This period of
rapid growth is referred to as the exponential growth phase. The growing cells
begin to deplete nutrients and wastes begin to accumulate. This leads to
stationary growth phase, during which growth continues slowly but the
number of viable cells does not increase because any increase in cell number
due to growth is balanced by cell death. Finally when nutrients are sufficiently
depleted and enough wastes have accumulated, the culture enters the death
phase, during which cells die rapidly.
Review the many ways in which microbes process oxygen by completing each
sentence. Then, please arrange the sentences in a logical order Correct
Ans - With respect to oxygen requirements, an aerobe can use gaseous
oxygen and possesses enzymes to process toxic oxygen products.
1
Expanding on this classification, an obligate aerobe cannot grow without
oxygen.
2
Microaerophiles do not grow at normal atmospheric oxygen concentrations,
but they do require very minute concentrations of oxygen for metabolism.
3
Still other organisms, called facultative anaerobes, can grow with or without
oxygen, but grow faster when oxygen is present.
4
Anaerobes represent a final group of organisms, whose members lack the
required enzymes needed for using oxygen in respiration and may not be able
to tolerate any free oxygen in their environment (obligate anaerobes).
