BIOS 242 MIDTERM EXAM
VERIFIED STUDY QUESTIONS
AND ANSWERS |A+ GRADED
Which of the following is true of virions?
A. They may include an envelope.
B. They always include nucleic acid.
C. They always include a protein capsid.
D. All the above. ✅They may include an envelope.
They always include nucleic acid.
They always include a protein capsid.
All of these are correct.
Which of the following drugs targets construction of the peptidoglycan cell wall?
✅Beta-lactams.
In which habitat would you most likely find archaea?
A. acidic hot springs.
B. great salt lake.
C. deep sea waters.
D. all the above. ✅acidic hot springs.
great salt lake.
deep sea waters.
Put the following stages of a lytic replication cycle in order from earliest to latest.
I. Synthesis.
II. Assembly.
III. Attachment.
IV. Release.
Entry. ✅III, V, I, II, VI
When placed in a hypotonic solution .
bacterial cells survive because of their cell walls. ✅bacterial cells survive because of
their cell walls.
eukaryotic cells may burst.
water rushes into cells.
all of these are correct.
Explain how aerobic organisms tolerate the presence of oxygen in their metabolic
pathways despite its toxic properties. ✅Oxygen is toxic to organisms only because of
the highly reactive alternative forms of the molecule. These forms of oxygen can
accumulate in cells and damage them by oxidizing key cellular molecules and
, structures. to tolerate the presence of oxygen (to allow aerobic cellular respiration to
take place), cells must have ways of converting these toxic forms of oxygen to less
harmful molecules. Cells use a variety of enzymes to accomplish this. These enzymes
are superoxide dismutase (for elimination of the superoxide radical) and catalase and
peroxidase (for the removal of hydrogen peroxide from cells). By continuous use of
these enzymes, aerobic cells can use oxygen in their metabolism without suffering too
many of the adverse effects of oxygen. Likewise, one major reason obligate anaerobes
cannot tolerate any oxygen in their environment is the absence or reduced activity of
such enzymes in those cells.
Explain how temperature and pH levels can influence microbial infections in the human
body. ✅ll microbes have particular ranges of temperature and pH within which they
exist. When the temperature or pH of their environment falls outside this range, their
growth is inhibited, and they may even die as a result of the adverse conditions.
Therefore, only those microbes whose pH and temperature requirements match those
conditions found in the human body will be able to grow and reproduce there. For
example, because the temperature of the human body is 37°C, only mesophiles can
reproduce there. In addition, the pH of most tissues and fluids in the body is 6.5-7.5,
which matches the pH requirements of neutrophiles. Therefore, it is not surprising that
most human pathogens are mesophiles and neutrophiles. However, this is not always
the case. Some microbes have adapted to environments that would otherwise be
extremely hostile to most microbes. A good example is the bacterium Helicobacter
pylori, which is able to live in the extremely acidic conditions of the stomach by
secreting substances that help to neutralize the acid. The result is an infection that can
lead to stomach ulcers.
Genetic methods of detecting microorganisms reveal that the number of bacterial
species in nature exceeds previous estimates by several orders of magnitude. In the
human mouth, for example, it is estimated that 500-700 microbial species are normally
present. Explain why previous estimates were low. ✅Previous estimates of microbial
diversity were largely based on the ability to detect microbes in samples handled in a
typical laboratory setting. In most cases, laboratory conditions represent a narrow range
of growth parameters, including temperature range, oxygen and other gas levels, and
spectrum of nutrients. Even in cases where attempts are made to simulate the normal
conditions for microbes (e.g., providing a high-pressure environment for organisms
collected from hyperbaric environment), microorganisms must frequently tolerate
fluctuations in the growth environment or even exposure to extremely adverse
conditions for short periods of time. Organisms that are intolerant of significant
VERIFIED STUDY QUESTIONS
AND ANSWERS |A+ GRADED
Which of the following is true of virions?
A. They may include an envelope.
B. They always include nucleic acid.
C. They always include a protein capsid.
D. All the above. ✅They may include an envelope.
They always include nucleic acid.
They always include a protein capsid.
All of these are correct.
Which of the following drugs targets construction of the peptidoglycan cell wall?
✅Beta-lactams.
In which habitat would you most likely find archaea?
A. acidic hot springs.
B. great salt lake.
C. deep sea waters.
D. all the above. ✅acidic hot springs.
great salt lake.
deep sea waters.
Put the following stages of a lytic replication cycle in order from earliest to latest.
I. Synthesis.
II. Assembly.
III. Attachment.
IV. Release.
Entry. ✅III, V, I, II, VI
When placed in a hypotonic solution .
bacterial cells survive because of their cell walls. ✅bacterial cells survive because of
their cell walls.
eukaryotic cells may burst.
water rushes into cells.
all of these are correct.
Explain how aerobic organisms tolerate the presence of oxygen in their metabolic
pathways despite its toxic properties. ✅Oxygen is toxic to organisms only because of
the highly reactive alternative forms of the molecule. These forms of oxygen can
accumulate in cells and damage them by oxidizing key cellular molecules and
, structures. to tolerate the presence of oxygen (to allow aerobic cellular respiration to
take place), cells must have ways of converting these toxic forms of oxygen to less
harmful molecules. Cells use a variety of enzymes to accomplish this. These enzymes
are superoxide dismutase (for elimination of the superoxide radical) and catalase and
peroxidase (for the removal of hydrogen peroxide from cells). By continuous use of
these enzymes, aerobic cells can use oxygen in their metabolism without suffering too
many of the adverse effects of oxygen. Likewise, one major reason obligate anaerobes
cannot tolerate any oxygen in their environment is the absence or reduced activity of
such enzymes in those cells.
Explain how temperature and pH levels can influence microbial infections in the human
body. ✅ll microbes have particular ranges of temperature and pH within which they
exist. When the temperature or pH of their environment falls outside this range, their
growth is inhibited, and they may even die as a result of the adverse conditions.
Therefore, only those microbes whose pH and temperature requirements match those
conditions found in the human body will be able to grow and reproduce there. For
example, because the temperature of the human body is 37°C, only mesophiles can
reproduce there. In addition, the pH of most tissues and fluids in the body is 6.5-7.5,
which matches the pH requirements of neutrophiles. Therefore, it is not surprising that
most human pathogens are mesophiles and neutrophiles. However, this is not always
the case. Some microbes have adapted to environments that would otherwise be
extremely hostile to most microbes. A good example is the bacterium Helicobacter
pylori, which is able to live in the extremely acidic conditions of the stomach by
secreting substances that help to neutralize the acid. The result is an infection that can
lead to stomach ulcers.
Genetic methods of detecting microorganisms reveal that the number of bacterial
species in nature exceeds previous estimates by several orders of magnitude. In the
human mouth, for example, it is estimated that 500-700 microbial species are normally
present. Explain why previous estimates were low. ✅Previous estimates of microbial
diversity were largely based on the ability to detect microbes in samples handled in a
typical laboratory setting. In most cases, laboratory conditions represent a narrow range
of growth parameters, including temperature range, oxygen and other gas levels, and
spectrum of nutrients. Even in cases where attempts are made to simulate the normal
conditions for microbes (e.g., providing a high-pressure environment for organisms
collected from hyperbaric environment), microorganisms must frequently tolerate
fluctuations in the growth environment or even exposure to extremely adverse
conditions for short periods of time. Organisms that are intolerant of significant
