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BIOL 203 Microbiology LCC Final Exam
2025-26 | Actual Exam Questions With
Correct Verified Solutions
Explain the concept of osmosis. We know that the process of pickling, adding large
amounts of salt, causes changes in the food itself. A cucumber will shrink into a
pickle. But how does adding large amounts of salt affect microbes that may have
contaminated the jar of pickles?-correct-answer-What does the salt do to the
spoilage (bad) bacteria?
Osmosis is diffusion of water. Water will move from an area of high water
concentration to an area of low water concentration. Another way to look at it
would be to say that water follows solute. If you have two solutions and one has a
high concentration of solute then it also has a low concentration of water. If the
second solution has a low concentration of solute then it has a high concentration
of water. If water were able to move between these two solutions (but solute was
not) then water would travel from the solution with a higher concentration of
water to the solution with a lower concentration of water.
Microbes are everywhere and by growing on, consuming, and producing waste
products, they spoil our food. We can slow this process down by heating food up
to boiling temperatures to kill all microbes present and by refrigerating our food
to cool enough temperatures that microbial metabolism and microbial growth
slows.
,2|Page
The process of pickling using large amounts of salt (solute) to create a solution
(pickle juice) that has a low concentration of water. In comparison, any microbes
that get into the jar of pickles has a higher concentration of water inside their
cells. Due to osmosis, the water inside of the cell (high water concentration) will
diffuse out of the cell into the pickle juice (low water concentration.) The cell will
then shrivel and without water, metabolism and microbial growth will stop. Little
microbial growth results in little spoilage and a longer shelf life.
In the laboratory, imagine that you transfer bacteria X from one flask of tryptic soy
nutrient broth into another flask of tryptic soy nutrient broth. If you were then to
measure and plot the bacterial growth curve of bacteria X, would you would
notice a long lag phase? Why or why not?-correct-answer-What happens in the
lag phase? Is it being transferred to a new environment with different nutrients
that it would need to express different genes to utilize?
Bacterial growth in a contained environment (like a flask) will grow in 4 distinct
phases.
The first phase is Lag Phase where the bacteria are getting acclimated to their
environment. There is no net increase in the number of microbes. This means
they are sensing what type of nutrition is available and tailoring their gene
expression to use it. They might have the genes to metabolize glucose, sucrose,
and lactose, but it doesn't make sense to express the genes for glucose and
sucrose if only lactose is present because this would waste APT energy. So in an
environment with only lactose, those microbes would be expressing genes needed
to break down and harvest energy from lactose. If they had previously been in an
,3|Page
environment with lactose, then they wouldn't need much time to acclimate
because they would already be actively expressing the lactose genes and we
would observe a very short lag phase.
Imagine instead that they had been in an environment with only sucrose. Now
they need to stop expressing sucrose genes and start expressing lactose genes.
This would take longer and we would notice a significant lag phase.
So in our example above, we would not notice a long lag phase because the
bacteria were already acclimated to the nutrients in tryptic soy broth because
they came from tryptic soy broth.
Once acclimated, the bacteria would grow optimally in Log Phase. There is a great
increase in the number of microbes. This rapid growth will result in a decrease of
available nutrients and an increase in waste products causing growth to slow. The
amount of cells produced by binary fission will soon equal the amount of cells that
die due to lack of nutrients and was
Consider obligate anaerobes, facultative anaerobes, and aerotolerant anaerobes.
In what way are they all similar? In what way are they all different? Be specific and
explain your answer for full credit.-correct-answer-They are similar by all having
to do with living with oxygen, good or bad.
They are different because obligate anaerobes cannot survive with oxygen,
facultative anaerobes use oxygen to grow but can also live without it, and
aerotolerant anaerobes don't use oxygen but can still live with it.
, 4|Page
Humans live symbiotically with many, many different microbes. Describe a human-
microbe relationship that is considered mutualistic and then describe one that is
considered parasitic.-correct-answer-A human-microbe relationship that is
considered mutalistic is bacteria, they can prevent pathogenic organisms from
taking over an area, while the human offers them a place to live and survive.
A human-microbe relationship that is considered parasitic is parasitism, this
relationship harms the host and is beneficial to the parasite. The kinds of harm
can be anywhere from superficial damage, rapid damage, to significant damage.
There are microbes that call your intestines home. Using the terms you learned in
this unit, we might describe them as obligate anaerobes, alkaliphiles, mesophiles,
etc. There are microbes that call your skin home. Use at least 3-4 terms from this
unit to describe skin microbes and explain why you selected each term.-correct-
answer-What do we call bacteria that grow at those temperatures?
Human skin is very salty (from sweat) so skin microbes could be called halophiles.
The skin is exposed to oxygen in our atmosphere so skin microbes could be
obligate aerobes, facultative anaerobes, or possibly aerotolerant anaerobes.
The skin is slightly acidic (from oil or sebum) so skin microbes could be
acidophiles.
BIOL 203 Microbiology LCC Final Exam
2025-26 | Actual Exam Questions With
Correct Verified Solutions
Explain the concept of osmosis. We know that the process of pickling, adding large
amounts of salt, causes changes in the food itself. A cucumber will shrink into a
pickle. But how does adding large amounts of salt affect microbes that may have
contaminated the jar of pickles?-correct-answer-What does the salt do to the
spoilage (bad) bacteria?
Osmosis is diffusion of water. Water will move from an area of high water
concentration to an area of low water concentration. Another way to look at it
would be to say that water follows solute. If you have two solutions and one has a
high concentration of solute then it also has a low concentration of water. If the
second solution has a low concentration of solute then it has a high concentration
of water. If water were able to move between these two solutions (but solute was
not) then water would travel from the solution with a higher concentration of
water to the solution with a lower concentration of water.
Microbes are everywhere and by growing on, consuming, and producing waste
products, they spoil our food. We can slow this process down by heating food up
to boiling temperatures to kill all microbes present and by refrigerating our food
to cool enough temperatures that microbial metabolism and microbial growth
slows.
,2|Page
The process of pickling using large amounts of salt (solute) to create a solution
(pickle juice) that has a low concentration of water. In comparison, any microbes
that get into the jar of pickles has a higher concentration of water inside their
cells. Due to osmosis, the water inside of the cell (high water concentration) will
diffuse out of the cell into the pickle juice (low water concentration.) The cell will
then shrivel and without water, metabolism and microbial growth will stop. Little
microbial growth results in little spoilage and a longer shelf life.
In the laboratory, imagine that you transfer bacteria X from one flask of tryptic soy
nutrient broth into another flask of tryptic soy nutrient broth. If you were then to
measure and plot the bacterial growth curve of bacteria X, would you would
notice a long lag phase? Why or why not?-correct-answer-What happens in the
lag phase? Is it being transferred to a new environment with different nutrients
that it would need to express different genes to utilize?
Bacterial growth in a contained environment (like a flask) will grow in 4 distinct
phases.
The first phase is Lag Phase where the bacteria are getting acclimated to their
environment. There is no net increase in the number of microbes. This means
they are sensing what type of nutrition is available and tailoring their gene
expression to use it. They might have the genes to metabolize glucose, sucrose,
and lactose, but it doesn't make sense to express the genes for glucose and
sucrose if only lactose is present because this would waste APT energy. So in an
environment with only lactose, those microbes would be expressing genes needed
to break down and harvest energy from lactose. If they had previously been in an
,3|Page
environment with lactose, then they wouldn't need much time to acclimate
because they would already be actively expressing the lactose genes and we
would observe a very short lag phase.
Imagine instead that they had been in an environment with only sucrose. Now
they need to stop expressing sucrose genes and start expressing lactose genes.
This would take longer and we would notice a significant lag phase.
So in our example above, we would not notice a long lag phase because the
bacteria were already acclimated to the nutrients in tryptic soy broth because
they came from tryptic soy broth.
Once acclimated, the bacteria would grow optimally in Log Phase. There is a great
increase in the number of microbes. This rapid growth will result in a decrease of
available nutrients and an increase in waste products causing growth to slow. The
amount of cells produced by binary fission will soon equal the amount of cells that
die due to lack of nutrients and was
Consider obligate anaerobes, facultative anaerobes, and aerotolerant anaerobes.
In what way are they all similar? In what way are they all different? Be specific and
explain your answer for full credit.-correct-answer-They are similar by all having
to do with living with oxygen, good or bad.
They are different because obligate anaerobes cannot survive with oxygen,
facultative anaerobes use oxygen to grow but can also live without it, and
aerotolerant anaerobes don't use oxygen but can still live with it.
, 4|Page
Humans live symbiotically with many, many different microbes. Describe a human-
microbe relationship that is considered mutualistic and then describe one that is
considered parasitic.-correct-answer-A human-microbe relationship that is
considered mutalistic is bacteria, they can prevent pathogenic organisms from
taking over an area, while the human offers them a place to live and survive.
A human-microbe relationship that is considered parasitic is parasitism, this
relationship harms the host and is beneficial to the parasite. The kinds of harm
can be anywhere from superficial damage, rapid damage, to significant damage.
There are microbes that call your intestines home. Using the terms you learned in
this unit, we might describe them as obligate anaerobes, alkaliphiles, mesophiles,
etc. There are microbes that call your skin home. Use at least 3-4 terms from this
unit to describe skin microbes and explain why you selected each term.-correct-
answer-What do we call bacteria that grow at those temperatures?
Human skin is very salty (from sweat) so skin microbes could be called halophiles.
The skin is exposed to oxygen in our atmosphere so skin microbes could be
obligate aerobes, facultative anaerobes, or possibly aerotolerant anaerobes.
The skin is slightly acidic (from oil or sebum) so skin microbes could be
acidophiles.
