MMG 421 - Exam 3 Questions Well Answered Graded A+
chemolithotrophic bacteria and archaea obtain energy and electrons from inorganic sources -
Answers true
PMF refers to the process of e- shuttling from an e- donor to NAD+ - Answers false
protons
purple sulfur bacteria and green sulfur bacteria utilize H2S as e- donor in phototrophy, and as a
result produce elemental sulfur as a product of their photosynthesis, a process called
anoxygenic photosynthesis - Answers true
the redox potential (also called reduction potential) of an element participating in a respiration
metabolism represents its potential to donate e- in that metabolism, and is measured in units of
volts - Answers true
in reverse e- flow in a cell membrane, an e- originating from an external e- donor moves towards
a more electropositive e- acceptor - Answers false
electronegative instead of electropositive
reverse e- flow is required by many, if not most, chemolithotrophs other than hydrogen oxidizers
and is facilitated by PMF - Answers true
a dissimilatory metabolic rxn is one in which the metabolic end product of the redox rxn is
incorporated into microbial biomass - Answers false
assimilatory instead of dissimilatory
a mixotroph is a microorganism that utilizes an inorganic chemical for e- and energy, but an
organic source of C - Answers true
a bacterial cell is able to detect concentration gradients of chemicals over space (distance)
through tumble/run random-walk motion - Answers false
over time instead of over space
a high N:P ratio in the aquatic environments of cyanobacteria is favorable for nitrogen fixation
because of the high energy demand of this metabolism - Answers false
,low N:P instead of high N:P
an e- acceptor in respirations, oxygen provides the least energy yield when coupled with any
given e- donor, compared to all other e- acceptors such as nitrate, Fe3+, sulfate, etc. - Answers
false
high energy yield instead of least energy yield
sulfide can be oxidized both aerobically and anaerobically to sulfate by microorganisms to
complete the sulfur cycle - Answers true
nitrifiers are microorganisms that reduce nitrate to nitrogen gas (via intermediates) under
anaerobic conditions. - Answers false
denitrifiers instead of nitrifiers
denitrifiers are microorganisms that oxidize ammonium to nitrate (via intermed) typically under
aerobic conditions - Answers false
nitrifiers instead of denitrifiers
nitrate can serve as an e- acceptor in anaerobic oxidation of methane and elemental sulfur,
thereby coupling nitrogen cycle transformations to booth the carbon and sulfur cycles via
microbial metabolisms - Answers true
anammox refers to anaerobic oxidation of ammonium to nitrogen gas by planctomycete
bacteria in the oceans with nitrate as e- acceptor, and represents a key mechanism for
transformation of ammonium in deep ocean water - Answers true
nitrogen fixation is a high energy yielding microbial metabolism, surpassing even aerobic,
oxidative respiration in gibbs free energy - Answers false
demanding instead of yielding
in dissimilatory respiration, microorganisms incorporate the e- acceptor into biomass to form
part of the cell - Answers false
, assimilatory instead of dissimilatory
bioremediation of uranium+6 in ground water with in situ geobacter bacterial respiratory
metabolism is an example of assimilatory metal reduction - Answers false
dissimilatory instead of assimilatory
dehalorespiration is a reductive metabolic property of respiration by dehalococcoides
ethenogenes where chlorinated hydrocarbons such as trichloroethene pollutants serve as e-
acceptors - Answers true
many autotrophic bacteria fix inorganic carbon without the use of light through multiple fixation
pathways - Answers true
generation of nitrous oxide (N2O) from agricultural soils is an indication of incomplete
denitrification of nitrate to nitrogen gas by the resident denitrifying bacterial community in those
soils - Answers true
The chemiosmotic theory of life postulates which of the following structural and chemical
elements of cells:
A. The cell membrane, membrane potential, and systems to import and export solutes and ions
B. A system of reduction of electron donors and electron transport within and near the
membrane, causing membrane potential and charge
C. Proton motive force and reducing capacity
D. A mode for synthesis of ATP with membrane-embedded ATP synthase, one of nature's few
true "wheels"
E. All of the above - Answers E. all of the above
In the microbial metabolism H2S + O2 > SO4 + H2O, the compound H2S has what role?
A. Provides chemical energy
B. Electron acceptor
C. Electron donor
D. Carbon source
chemolithotrophic bacteria and archaea obtain energy and electrons from inorganic sources -
Answers true
PMF refers to the process of e- shuttling from an e- donor to NAD+ - Answers false
protons
purple sulfur bacteria and green sulfur bacteria utilize H2S as e- donor in phototrophy, and as a
result produce elemental sulfur as a product of their photosynthesis, a process called
anoxygenic photosynthesis - Answers true
the redox potential (also called reduction potential) of an element participating in a respiration
metabolism represents its potential to donate e- in that metabolism, and is measured in units of
volts - Answers true
in reverse e- flow in a cell membrane, an e- originating from an external e- donor moves towards
a more electropositive e- acceptor - Answers false
electronegative instead of electropositive
reverse e- flow is required by many, if not most, chemolithotrophs other than hydrogen oxidizers
and is facilitated by PMF - Answers true
a dissimilatory metabolic rxn is one in which the metabolic end product of the redox rxn is
incorporated into microbial biomass - Answers false
assimilatory instead of dissimilatory
a mixotroph is a microorganism that utilizes an inorganic chemical for e- and energy, but an
organic source of C - Answers true
a bacterial cell is able to detect concentration gradients of chemicals over space (distance)
through tumble/run random-walk motion - Answers false
over time instead of over space
a high N:P ratio in the aquatic environments of cyanobacteria is favorable for nitrogen fixation
because of the high energy demand of this metabolism - Answers false
,low N:P instead of high N:P
an e- acceptor in respirations, oxygen provides the least energy yield when coupled with any
given e- donor, compared to all other e- acceptors such as nitrate, Fe3+, sulfate, etc. - Answers
false
high energy yield instead of least energy yield
sulfide can be oxidized both aerobically and anaerobically to sulfate by microorganisms to
complete the sulfur cycle - Answers true
nitrifiers are microorganisms that reduce nitrate to nitrogen gas (via intermediates) under
anaerobic conditions. - Answers false
denitrifiers instead of nitrifiers
denitrifiers are microorganisms that oxidize ammonium to nitrate (via intermed) typically under
aerobic conditions - Answers false
nitrifiers instead of denitrifiers
nitrate can serve as an e- acceptor in anaerobic oxidation of methane and elemental sulfur,
thereby coupling nitrogen cycle transformations to booth the carbon and sulfur cycles via
microbial metabolisms - Answers true
anammox refers to anaerobic oxidation of ammonium to nitrogen gas by planctomycete
bacteria in the oceans with nitrate as e- acceptor, and represents a key mechanism for
transformation of ammonium in deep ocean water - Answers true
nitrogen fixation is a high energy yielding microbial metabolism, surpassing even aerobic,
oxidative respiration in gibbs free energy - Answers false
demanding instead of yielding
in dissimilatory respiration, microorganisms incorporate the e- acceptor into biomass to form
part of the cell - Answers false
, assimilatory instead of dissimilatory
bioremediation of uranium+6 in ground water with in situ geobacter bacterial respiratory
metabolism is an example of assimilatory metal reduction - Answers false
dissimilatory instead of assimilatory
dehalorespiration is a reductive metabolic property of respiration by dehalococcoides
ethenogenes where chlorinated hydrocarbons such as trichloroethene pollutants serve as e-
acceptors - Answers true
many autotrophic bacteria fix inorganic carbon without the use of light through multiple fixation
pathways - Answers true
generation of nitrous oxide (N2O) from agricultural soils is an indication of incomplete
denitrification of nitrate to nitrogen gas by the resident denitrifying bacterial community in those
soils - Answers true
The chemiosmotic theory of life postulates which of the following structural and chemical
elements of cells:
A. The cell membrane, membrane potential, and systems to import and export solutes and ions
B. A system of reduction of electron donors and electron transport within and near the
membrane, causing membrane potential and charge
C. Proton motive force and reducing capacity
D. A mode for synthesis of ATP with membrane-embedded ATP synthase, one of nature's few
true "wheels"
E. All of the above - Answers E. all of the above
In the microbial metabolism H2S + O2 > SO4 + H2O, the compound H2S has what role?
A. Provides chemical energy
B. Electron acceptor
C. Electron donor
D. Carbon source
