BIO 261 Exam 1 – Powell Final Test
Questions and All Accurate Answers
2025-2026 Updated.
In what ways are microorganisms important to humans? - Answer They're important in
fermentation reactions, they produce biofuel
Studying microorganisms help with vaccination and antibiotic therapy
We use microorganisms to purify our water
Used in pasteurization so that food is safe to eat
What is a bacterial colony and how is one formed? - Answer A colony forms by placing a
single microbial cell on a solid nutrient medium where it can grow and divide into millions of
cells.
How can you get a pure culture of bacteria and why are pure cultures important? - Answer
You have a get microorganisms in a pure culture in order to identify them. You would see a
whole bunch of different kinds of organisms without having pure culture.
A pure culture is accomplished by spreading bacteria on the surface of a solid medium so a
single cell occupies an isolated portion. The single cell will go through multiplication
Where do you find microorganisms and do they typically live in a pure culture? - Answer
Anywhere... they're all over the place
They do not typically live in a pure culture
What cellular structures distinguish prokaryotic and eukaryotic cells? - Answer Prokaryotes
have plasmids, nucleoid, and normally a single circular chromosome
Eukaryotes have a nucleus and membrane bound organelles (mitochondria, golgi, endoplasmic
reticulum, etc). They have larger and more DNA and linear chromosomes
Eukaryotic cells have 80S ribosomes, bacterial cells have 70S ribosomes
What are some differences between a cell wall and a cell membrane? - Answer The cell
membrane is a phospholipid bilayer that separates the cell from its environment; all cells have
one. Its main function is selective permeability, choosing what goes in and what goes out of the
cell
The cell wall provides structural support to the cell; not all cells have one
In what types of organisms would you expect to find cell walls and/or cell membranes? - Answer
cell membranes are found in all cells
cell walls are found in plants and some bacteria, fungi, and archaea
,How has the earth changed over its history? How have microorganisms contributed to these
changes? - Answer Earth is 4.6 billion years old, and the first cells appeared between 3.8-4.3
bya. The atmosphere was anoxic (no oxygen) until abour 2.6 bya when cyanobacteria (able to
undergo photosynthesis and nitrogen fixation) oxygenated the earth. The plants and the
animals were able to evolve after that
Name the three domains of life. Which of these contain eukaryotic life forms? How are they
similar and different? - Answer Bacteria
Archaea
Eukarya (contains eukaryotic life forms such as fungi (yeasts and molds), protists, animals, and
plants)
They all are living and have at least one cell that contains genetic information. Bacteria and
Archaea are prokaryotic, Eukarya is eukaryotic. Eukarya is the only kingdom that includes
multicellular organisms (though unicellular organisms can be eukaryotic as well). All descended
from the last universal common ancestor
Why were cyanobacteria so important in the evolution of life on Earth? What is a genus name of
a cyanobacterium and what is unique about these organisms? - Answer Without
cyanobacteria, the earth would not have been oxygenated. There would be no plants or
animals.
Example of a genus name: Anabeana
How do microbes contribute to the nutrition of animals such as humans and cows? - Answer
The bacteria in our large intestines break down large carbohydrates and produce vitamins and
other nutrients
Cellulose-degrading microbes in the rumens of cows allow them to receive nutrients from the
plants they eat
Describe several ways in which microorganisms are important in the food and agricultural
industries - Answer They are used to pasteurize food to make it safe to eat
They are used in fermented and dairy products
Nitrogen-fixing (taking nitrogen out of the air and converting it to ammonia in the soil) bacteria
is what allows plants to grow
What is wastewater treatment and why is it important? - Answer Microbes take the poop in
wastewater and convert it to carbon dioxide and water, which purifies the water. Without the
cleaning of wastewater, our water wouldn't be pure, which would cause a lot of health issues
What is the difference between magnification and resolution? - Answer Magnification is the
ability to enlarge an image, while resolution is the ability to distinguish two adjacent objects as
distinct and separate
, What is the function of staining in light microscopy? - Answer It increases the contrast for
bright-field microscopy and allows us to see the specimen better
What color will a gram-negative cell be after gram staining by the conventional method? What
about gram positive? Why? - Answer Gram-negative bacteria (thin peptidoglycan) appear
pink and gram-positive bacteria (thick peptidoglycan cell walls) appear purple-violet. This is
because of the differences in cell wall structure.
What are the steps of a gram stain and the function of each reagent? - Answer 1. Flood the
heat-fixed smear with crystal violet (primary stain for cells to be purple) for 1 minute
2. Add iodine solution (complexes with the crystal violet inside of the cells, which are all still
purple at this point) for 1 minute
3. Decolorize the gram-negative cells with alcohol (removes the CV-I complex for gram-negative
cells) for 20 seconds
4. Counterstain with safranin (red stain that allows you to see the gram-negative cells) for 1-2
minutes
What major advantage does phase-contrast microscopy have over staining? - Answer You
can see organisms when they are alive
How can cells be made to fluoresce? - Answer they have quorom sensing
What are the major differences between electron microscopes and light microscopes? - Answer
Electron microscopes use electrons as a source to see specimens instead of light. This means
that electron microscopes have a much larger resolving power due to a smaller wavelength
The path of light in a light microscope is bottom to top, and the path of electrons in an electron
microscope is top to bottom
What type of microscope would be used to view the 3D features of a cell? What about the
internal parts of a cell? Why? - Answer 3D features = scanning electron microscope
Internal parts = transmission electron microscope
Electron microscopes are the microscopes that will let you see these structures because of their
strong resolving power
Explain how Pasteur disproved spontaneous generation (the theory that life came from nothing)
- Answer He conducted an experiment where he pouring a nonsterile liquid into a swan-
necked flask. The neck of the flask was drawn out in a flame, and the liquid was sterilized by
extensive heating. Steam was forced out of the open end of the flask, and the liquid slowly
cooled. In a few days, the flask neck became contaminated with dust and microorganisms from
air that was trapped. If the flask was gently tipped, the microbe-laden dust would mix with the
Questions and All Accurate Answers
2025-2026 Updated.
In what ways are microorganisms important to humans? - Answer They're important in
fermentation reactions, they produce biofuel
Studying microorganisms help with vaccination and antibiotic therapy
We use microorganisms to purify our water
Used in pasteurization so that food is safe to eat
What is a bacterial colony and how is one formed? - Answer A colony forms by placing a
single microbial cell on a solid nutrient medium where it can grow and divide into millions of
cells.
How can you get a pure culture of bacteria and why are pure cultures important? - Answer
You have a get microorganisms in a pure culture in order to identify them. You would see a
whole bunch of different kinds of organisms without having pure culture.
A pure culture is accomplished by spreading bacteria on the surface of a solid medium so a
single cell occupies an isolated portion. The single cell will go through multiplication
Where do you find microorganisms and do they typically live in a pure culture? - Answer
Anywhere... they're all over the place
They do not typically live in a pure culture
What cellular structures distinguish prokaryotic and eukaryotic cells? - Answer Prokaryotes
have plasmids, nucleoid, and normally a single circular chromosome
Eukaryotes have a nucleus and membrane bound organelles (mitochondria, golgi, endoplasmic
reticulum, etc). They have larger and more DNA and linear chromosomes
Eukaryotic cells have 80S ribosomes, bacterial cells have 70S ribosomes
What are some differences between a cell wall and a cell membrane? - Answer The cell
membrane is a phospholipid bilayer that separates the cell from its environment; all cells have
one. Its main function is selective permeability, choosing what goes in and what goes out of the
cell
The cell wall provides structural support to the cell; not all cells have one
In what types of organisms would you expect to find cell walls and/or cell membranes? - Answer
cell membranes are found in all cells
cell walls are found in plants and some bacteria, fungi, and archaea
,How has the earth changed over its history? How have microorganisms contributed to these
changes? - Answer Earth is 4.6 billion years old, and the first cells appeared between 3.8-4.3
bya. The atmosphere was anoxic (no oxygen) until abour 2.6 bya when cyanobacteria (able to
undergo photosynthesis and nitrogen fixation) oxygenated the earth. The plants and the
animals were able to evolve after that
Name the three domains of life. Which of these contain eukaryotic life forms? How are they
similar and different? - Answer Bacteria
Archaea
Eukarya (contains eukaryotic life forms such as fungi (yeasts and molds), protists, animals, and
plants)
They all are living and have at least one cell that contains genetic information. Bacteria and
Archaea are prokaryotic, Eukarya is eukaryotic. Eukarya is the only kingdom that includes
multicellular organisms (though unicellular organisms can be eukaryotic as well). All descended
from the last universal common ancestor
Why were cyanobacteria so important in the evolution of life on Earth? What is a genus name of
a cyanobacterium and what is unique about these organisms? - Answer Without
cyanobacteria, the earth would not have been oxygenated. There would be no plants or
animals.
Example of a genus name: Anabeana
How do microbes contribute to the nutrition of animals such as humans and cows? - Answer
The bacteria in our large intestines break down large carbohydrates and produce vitamins and
other nutrients
Cellulose-degrading microbes in the rumens of cows allow them to receive nutrients from the
plants they eat
Describe several ways in which microorganisms are important in the food and agricultural
industries - Answer They are used to pasteurize food to make it safe to eat
They are used in fermented and dairy products
Nitrogen-fixing (taking nitrogen out of the air and converting it to ammonia in the soil) bacteria
is what allows plants to grow
What is wastewater treatment and why is it important? - Answer Microbes take the poop in
wastewater and convert it to carbon dioxide and water, which purifies the water. Without the
cleaning of wastewater, our water wouldn't be pure, which would cause a lot of health issues
What is the difference between magnification and resolution? - Answer Magnification is the
ability to enlarge an image, while resolution is the ability to distinguish two adjacent objects as
distinct and separate
, What is the function of staining in light microscopy? - Answer It increases the contrast for
bright-field microscopy and allows us to see the specimen better
What color will a gram-negative cell be after gram staining by the conventional method? What
about gram positive? Why? - Answer Gram-negative bacteria (thin peptidoglycan) appear
pink and gram-positive bacteria (thick peptidoglycan cell walls) appear purple-violet. This is
because of the differences in cell wall structure.
What are the steps of a gram stain and the function of each reagent? - Answer 1. Flood the
heat-fixed smear with crystal violet (primary stain for cells to be purple) for 1 minute
2. Add iodine solution (complexes with the crystal violet inside of the cells, which are all still
purple at this point) for 1 minute
3. Decolorize the gram-negative cells with alcohol (removes the CV-I complex for gram-negative
cells) for 20 seconds
4. Counterstain with safranin (red stain that allows you to see the gram-negative cells) for 1-2
minutes
What major advantage does phase-contrast microscopy have over staining? - Answer You
can see organisms when they are alive
How can cells be made to fluoresce? - Answer they have quorom sensing
What are the major differences between electron microscopes and light microscopes? - Answer
Electron microscopes use electrons as a source to see specimens instead of light. This means
that electron microscopes have a much larger resolving power due to a smaller wavelength
The path of light in a light microscope is bottom to top, and the path of electrons in an electron
microscope is top to bottom
What type of microscope would be used to view the 3D features of a cell? What about the
internal parts of a cell? Why? - Answer 3D features = scanning electron microscope
Internal parts = transmission electron microscope
Electron microscopes are the microscopes that will let you see these structures because of their
strong resolving power
Explain how Pasteur disproved spontaneous generation (the theory that life came from nothing)
- Answer He conducted an experiment where he pouring a nonsterile liquid into a swan-
necked flask. The neck of the flask was drawn out in a flame, and the liquid was sterilized by
extensive heating. Steam was forced out of the open end of the flask, and the liquid slowly
cooled. In a few days, the flask neck became contaminated with dust and microorganisms from
air that was trapped. If the flask was gently tipped, the microbe-laden dust would mix with the
