MIC 102 UC DAVIS QUESTIONS AND ANSWERS
What is a microbe? - Answers -"free-living organisms so small that they are only visible
under the microscope"
Are their exceptions to the definition to microbes? - Answers -Yes, some microbes are
hug, not free-living, or organisms
What is LUCA? And how does it relate to microbes? - Answers -Last Universal
Common Ancestor is thought to be what all organisms have evolved from over 4 billion
years. Specifically though, the LUCA is thought to be a microbe. Can determine
relationships from the small subunit (16S) rRNA gene
Name three characteristics of LUCA - Answers -The LUCA and common species today
share 1) DNA as genetic material 2)Protein and RNA 3) Lipid Membrane
Explain how the three domain tree is different from the ring of life. - Answers -The three
domain tree groups the organisms into their three appropriate lineage (Bacteria,
Archaea, and Eukarya), Each developing linearly and separating with different
adaptations. Whereas a ring of life includes lineage from lateral gene transfer - the
organisms are really intertwined with one another and creating new species.
What are the pros and cons for microbes being small? - Answers -Pro: microbes can
maintain a high surface-to-volume ratio to maximize nutrient exchange.
Con: Easy targets for larger microbes/species.
How does cell shape influence cell metabolism? - Answers -High surface are to volume
ratio can increase metabolism of nutrients, which will in affect increase growth and
reproduction.
Compare and contrast the general structures of archaea, bacteria and eukaryotic
bacteria. - Answers -Prokaryotics: no nucleus
bacteria: have rod shaped, sphere shaped, and helixcal shapes
archaea: have sphereical and rod shaped organiams
Eukaryotes: have fungi, slime molds mircroscopic algae, and protozoa...Organelles
include nuclus, mitcochondria, and chloroplast.
Explain why cells must have a membrane - Answers -To make a selective barrier for
chemical diffusion and allow the primitive biological molecules to replicate and catalyze
reactions in a protected , favored environment.
Provide evidence for two cases of convergent evolution between bacteria and archaea
cell exteriors. - Answers -1. flagella, but they differ in their assembly and structure.
, 2. Pili: filamentous appendages, which will attach to host cells, transfer proteins and
nucleic acids to other cells and motility.
Why must bacteria cells be stained to cell them? - Answers -Because it is hard to
contrast the colorless cell and can;t be seen readily under the microscope. gram postive
stains purple and gram negative will stain red.
List advantages and disadvantages of light microscopy, fluorescence microscopy, and
electron microscopy. - Answers --Light microscopy: pro can see the small microbes and
structural makeup, cons need to gram stain the bacteria to differentiate the species,
which will kill them
-fluorescence microscopy: pro can target components in the cell or tissues by using dye
and emitting light at specific wavelength, con ?
-electron microscopy: pro can determine fine structural detail to make a 3D picture,
con:distort structure because shot with electron/proton.
Compare and contrast the cell envelopes of gram negative and gram positive bacteria. -
Answers -Gram Positive: have a thick cell wall/peptidoglycan layer then a cell
membrane. Have teichoic acid and lipoteichoic acid.
Gram negative: have two outer membranes with a thin cell wall/peptidoglycan layer in
the middle. Have lipopolysaccharide
What are some roles of the bacterial murein cell wall? - Answers -1. thicker walls limits
the passage of hydrophobic compounds.
2. Act as amour, and structural support.
Differences and similarities in the bacterial and archaeal cell membranes. - Answers -
The bacterial phospholipid bilayer has ester linkages, and two phospholipids
(hydrophillic heads and hydrophobic tails with two fatty acid chains).
The archaeal cell membrane can have either a phospholipid bilayer or monolayer
connected by ether linkages. The monolayer here however, with have 40 carbon
isopreniod groups(one straight chain from the outsides)
Predict mechanisms that could allow gram positive bacteria to become resistant to
penicillins. - Answers -Gram positive bacteria maybe could have developed thicker
peptidoglycan layers, or have developed another enzyme that cross-links the layers
together.
Differences and similarities in the bacterial and archaeal cell wall. - Answers -Archaea
do not have murein cell walls and protect themselves with just an S-layer. Cell walls of
archaea could be made up off pseudomurein (made up of polysasccarides or a type of
peptidoglycan.) - these will also stain gram positive.
Importance of hopanoids for bacteria. - Answers -Hopanoids are unsual lipids made by
only bacteria. These add rigidity and stability to the cell membrane. These are useful for
detecting bacteria.
What is a microbe? - Answers -"free-living organisms so small that they are only visible
under the microscope"
Are their exceptions to the definition to microbes? - Answers -Yes, some microbes are
hug, not free-living, or organisms
What is LUCA? And how does it relate to microbes? - Answers -Last Universal
Common Ancestor is thought to be what all organisms have evolved from over 4 billion
years. Specifically though, the LUCA is thought to be a microbe. Can determine
relationships from the small subunit (16S) rRNA gene
Name three characteristics of LUCA - Answers -The LUCA and common species today
share 1) DNA as genetic material 2)Protein and RNA 3) Lipid Membrane
Explain how the three domain tree is different from the ring of life. - Answers -The three
domain tree groups the organisms into their three appropriate lineage (Bacteria,
Archaea, and Eukarya), Each developing linearly and separating with different
adaptations. Whereas a ring of life includes lineage from lateral gene transfer - the
organisms are really intertwined with one another and creating new species.
What are the pros and cons for microbes being small? - Answers -Pro: microbes can
maintain a high surface-to-volume ratio to maximize nutrient exchange.
Con: Easy targets for larger microbes/species.
How does cell shape influence cell metabolism? - Answers -High surface are to volume
ratio can increase metabolism of nutrients, which will in affect increase growth and
reproduction.
Compare and contrast the general structures of archaea, bacteria and eukaryotic
bacteria. - Answers -Prokaryotics: no nucleus
bacteria: have rod shaped, sphere shaped, and helixcal shapes
archaea: have sphereical and rod shaped organiams
Eukaryotes: have fungi, slime molds mircroscopic algae, and protozoa...Organelles
include nuclus, mitcochondria, and chloroplast.
Explain why cells must have a membrane - Answers -To make a selective barrier for
chemical diffusion and allow the primitive biological molecules to replicate and catalyze
reactions in a protected , favored environment.
Provide evidence for two cases of convergent evolution between bacteria and archaea
cell exteriors. - Answers -1. flagella, but they differ in their assembly and structure.
, 2. Pili: filamentous appendages, which will attach to host cells, transfer proteins and
nucleic acids to other cells and motility.
Why must bacteria cells be stained to cell them? - Answers -Because it is hard to
contrast the colorless cell and can;t be seen readily under the microscope. gram postive
stains purple and gram negative will stain red.
List advantages and disadvantages of light microscopy, fluorescence microscopy, and
electron microscopy. - Answers --Light microscopy: pro can see the small microbes and
structural makeup, cons need to gram stain the bacteria to differentiate the species,
which will kill them
-fluorescence microscopy: pro can target components in the cell or tissues by using dye
and emitting light at specific wavelength, con ?
-electron microscopy: pro can determine fine structural detail to make a 3D picture,
con:distort structure because shot with electron/proton.
Compare and contrast the cell envelopes of gram negative and gram positive bacteria. -
Answers -Gram Positive: have a thick cell wall/peptidoglycan layer then a cell
membrane. Have teichoic acid and lipoteichoic acid.
Gram negative: have two outer membranes with a thin cell wall/peptidoglycan layer in
the middle. Have lipopolysaccharide
What are some roles of the bacterial murein cell wall? - Answers -1. thicker walls limits
the passage of hydrophobic compounds.
2. Act as amour, and structural support.
Differences and similarities in the bacterial and archaeal cell membranes. - Answers -
The bacterial phospholipid bilayer has ester linkages, and two phospholipids
(hydrophillic heads and hydrophobic tails with two fatty acid chains).
The archaeal cell membrane can have either a phospholipid bilayer or monolayer
connected by ether linkages. The monolayer here however, with have 40 carbon
isopreniod groups(one straight chain from the outsides)
Predict mechanisms that could allow gram positive bacteria to become resistant to
penicillins. - Answers -Gram positive bacteria maybe could have developed thicker
peptidoglycan layers, or have developed another enzyme that cross-links the layers
together.
Differences and similarities in the bacterial and archaeal cell wall. - Answers -Archaea
do not have murein cell walls and protect themselves with just an S-layer. Cell walls of
archaea could be made up off pseudomurein (made up of polysasccarides or a type of
peptidoglycan.) - these will also stain gram positive.
Importance of hopanoids for bacteria. - Answers -Hopanoids are unsual lipids made by
only bacteria. These add rigidity and stability to the cell membrane. These are useful for
detecting bacteria.
