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BICH 411 Final Exam new material (1
BICH 411 Final Exam new material (1
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BICH 411 Final Exam new materialWhat is nitrogen fixation?
a. The reduction of NO3− to NH4+.
b. The formation of NH4+ from N2 gas.
c. The oxidation of NH4+ to N2.
d. The oxidation of NH4+ to NO3−.
e. The formation of NO2− from NO3−. - ANS-B
Animals are totally dependent on plants and microorganisms for nitrogen fixation and
nitrate assimilation because animals:
a. do not have the reducing power (NADPH) to fix nitrogen.
b. lack the enzyme aminotransferase.
c. lack the enzymes to reduce N2 and NO3− to NH4+.
d. lack carbamoyl-phosphate synthetase I.
e. lack glutamate dehydrogenase. - ANS-C
Nitrifying bacteria obtain their chemical energy from:
a. the reduction of NO3− to NH4+.
b. the formation of NH4+ from N2 gas.
c. the oxidation of NH4+ to N2.
d. the oxidation of NH4+ to NO3−.
e. the formation of NO2− from NO3−. - ANS-D
Denitrifying bacteria are capable of all EXCEPT:
a. reducing NO3− to N2.
b. using NO3− as an electron acceptor in their energy-producing pathways.
c. oxidizing NH4+to NO3−.
d. reducing the combined-nitrogen levels.
e. being utilized in water treatment plants to reduce nitrogen entering lakes and sNitrate
assimilation occurs in two steps: reduction of nitrate to ____ and further
reductiontreams. - ANS-C
to ____.
a. ammonia; nitrogen
b. nitrogen; ammonia
c. nitrite; nitrogen
d. nitrite; ammonia
e. none are correct - ANS-D
,The correct sequence for electron-transport in nitrate reductase is:
A. NADH
B. −SH
C. FAD
D. Cyt b557
E. MoCo
F. NO3−
a. A, B, C, D, E, F
b. B, C, A, D, F, E
c. D, A, B, C, E, F
d. A, C, B, D, F, E
e. C, A, B, D, E, F - ANS-A
Nitrite reductase requires ____ electrons to reduce NO2− to NH4+ and the electrons
are provided in higher plants through photosynthesis as reduced ____.
a. 2; plastoquinone
b. 3; plastoquinone
c. 4; heme
d. 5; heme
e. 6; ferredoxin - ANS-E
Nitrogen fixation involves the enzyme ____ catalyzing the reaction:
N2 + 10 ____ + ____ e− → 2 NH4+ + H2
a. nitrate reductase; H2O; 6
b. nitrogenase; H+; 8
c. nitrogenase; H+; 2
d. nitrogen reductase; H2O; 6
e. none are true - ANS-B
All N2-fixing systems are nearly identical and have all of the requirements EXCEPT:
a. ATP.
b. O2-free conditions.
c. the enzyme nitrogenase.
d. strong reductant such as ferredoxin.
e. all are true. - ANS-E
The involvement of ATP in the nitrogenase complex is because ATP is needed to:
, a. provide electrons.
b. phosphorylate the enzyme.
c. break the N2 triple bond.
d. transfer electrons from ferredoxin.
e. all are true. - ANS-C
Control over nitrogenase activity is accomplished by which of the following?
a. ATP serves as an allosteric activator
b. AMP serves as an allosteric inhibitor
c. NH4+ prevents expression of the genes that encode nitrogenase
d. phosphorylation prevents activity
e. none of the above - ANS-C
N-acetylglutamate functions in ammonium incorporation into metabolic intermediates
as:
a. a coenzyme for glutamine synthetase (GS).
b. a competitive inhibitor for glutamine synthetase (GS).
c. an allosteric activator for carbamoyl-phosphate synthetase I (CPS-I).
d. the energy source needed for the reductive amination of α-ketoglutarate (α-KG) to
yield glutamate.
e. the substrate for the amination of the γ-glutamylphosphate. - ANS-C
What reaction does glutamate dehydrogenase (GDH) catalyze?
a. The reductive amination of α-ketoglutarate to yield glutamate.
b. Phosphorylation of carbamate to yield carbamoyl-phosphate.
c. The amidation of the γ-carboxyl group of glutamate to form glutamine.
d. The deadenylation of glutamine synthetase.
e. The adenylation of glutamine synthetase. - ANS-A
The reaction, glutamate + NAD(P)+ + H2O → NH4+ + α-ketoglutarate + NAD(P)H + H+,
is catalyzed by:
a. Nitrogenase.
b. carbamoyl-phosphate synthetase (CPS-I).
c. glutamate dehydrogenase (GDH).
d. glutamine synthetase (GS).
e. none are true. - ANS-C
Glutamine synthetase is activated by which of the following molecules?
a. glycine
b. AMP
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