Practice Questions Bioenergetics Bc 100 bioenergetics practice mcqs dec

1. Practice Questions
Bioenergetics
Dr T.Nyambo
Department of Biochemistry
School of Medicine
MUHAS
4 December 2016

2. Practice questions
A simple pathway has two steps: A  B  C
• ∆Go'
for A  B = +11.4 kJ/mol, and Keq is 10-2
∆Go'
for B  C = -22.8 kJ/mol, and Keq is 104
• a. What is the standard free energy change for
conversion of A to C? ________kJ/mol
2

3. Practice questions
The standard free energy of hydrolysis of acetyl CoA is -7.8
kcal/mole. The standard free energy of hydrolysis of ATP to
AMP and pyrophosphate is -7.3 kcal/mole. What is the
standard free energy for the reaction written below?
acetate + ATP + CoA ---> Acetyl CoA + AMP + Pyrophosphate
A. -0.5 kcal/mole
B. -7.8 kcal/mole
C. -15.1 kcal/mole
D. +0.5 kcal/mole
E. +15.1 kcal/mole
3

4. Practice questions
1.The free energy of hydrolysis of a compound must
be at least ________, in order for it to be
considered a "high-energy" compound.
A.-3 kcal/mol
B.-5 kcal/mol
C.-7 kcal/mol
D.-9 kcal/mol
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5. Practice questions
2.The standard free energy (DG°') of ATP
hydrolysis to ADP + Pi is about
A.+30 kJ/mol.
B.+14 kJ/mol
C.-14 kJ/mol
D.-30 kJ/mol
E.-62 kJ/mol.
5

6. Practice questions
3. The standard free energy(∆Go
’) of hydrolysis of acetyl CoA
is -7.8kcal/mole. The standard free energy of hydrolysis of
ATP to AMP and pyrophosphate is -7.3 kcal/mole. What is
the standard free energy for the reaction written below?
acetate + ATP + CoA  Acetyl CoA + AMP + Pyrophosphate
A.-0.5 kcal/mole
B. -7.8 kcal/mole
C. -15.1 kcal/mole
D.+0.5 kcal/mole
E. +15.1 kcal/mole
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7. Practice questions
4. High energy compounds include all of the
following EXCEPT:
A.Esters
B.Phosphate anhydrides
C.Enol phosphates (phosphoenol pyruvate)
D.Thioesters
E.Creatine phosphate
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8. Practice questions
5.Glucose 1-phosphate can be converted to fructose 6-
phosphate in the following two reactions. The value ΔGo’
for
the overall conversion is:
Glucose 1-phosphate  glucose 6-phosphate ΔGo
’ = -7.1kJ/mol
Glucose 6-phosphate  fructose 6-phosphate ΔGo
’ = -1.7kJ/mol
A.+5.5kJ/mol
B. +8.8 kJ/mol
C. –8.8kJ/mol
D. –5.5kJl/mol
E. -0.0 kJ/mol
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9. Practice questions
6. Coupled reactions involved in the trapping of free energy from fuel
molecules consist of
A. Two endergonic reactions, one of which has a higher standard free
energy change (∆Go
') than the other
B. Two exergonic reactions, one of which has a lower ∆Go
' than the
other
C. One exergonic reaction coupled to an endergonic reaction, which
has a lower ∆Go
' than the exergonic reaction
D. One endergonic reaction coupled to an exergonic reaction, which
has a lower ∆Go
' than the endergonic reaction
E. None of the above
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10. Practice questions
7.What part of the electron transport chain does
cyanide (CN-
) react with?
A.Complex I
B.Complex II
C.Complex III
D.Complex IV
E.Cytochrome C
10

11. Practice questions
9. What is the terminal component in the electron
transport chain that reduces oxygen to form water
and that can be poisoned by cyanide?
A.Cytochrome c1
B.Cytochrome oxidase
C.Cytochrome c
D.Coenzyme Q
E.Cytochrome b
11

12. Practice questions
10. ATP is considered to be the universal source of
energy for endergonic reactions but is not the
storage form of energy under physiological
conditions. Why?
A.The actual free energy of hydrolysis of ATP is only
-11 to -12 kcal.
B.ATP is not located in the cytoplasm where most
endergonic reactions occur.
C.The half-life of ATP is too short.
D.The synthesis rate for ATP is not efficient.
E.None of the above
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13. Practice questions
11.What is the value of Δ Go' for the pathway A 
B  C D?
Reaction Δ Go'
B  A +20 kJ/mol
C  A +20 kJ/mol
C  D -60kJ/mol
A. +40
B. +20
C. -40
D. -60
E. –80 13

14. Practice questions
12. Glucose 1-phosphate can be converted to fructose 6-phosphate in
the following two reactions. What is the value of D Go
’ for the overall
conversion?
Glucose 1-phosphate ß  glucose 6-phosphate ∆ Go
’ = -1.7 kcal/mol
Glucose 6-phosphate ß  fructose 6-phosphate ∆ Go
’ = -0.4 kcal/mol
A. -2.1 kcal/mol
B. -1.3 kcal/mol
C. -0.0 kcal/mol
D. +1.3 kcal/mol
E. +2.1 kcal/mol
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15. Practice Questions
• 13. In the electron transport scheme below, which
electron carrier is missing?NADH FMNH2??
cytochromes O2
A.Vitamin K
B.Vitamin C
C.Ferridoxin
D.Ubiquinone (coenzyme Q)
E.NADPH
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16. Practice questions
14.The actual free energy change (∆G for a reaction is
equal to
Α.∆G’ = ∆ Go’+ RTlog10 {[Products]/[Reactants]}
Β.∆G’ = ∆ Go’+ RTln {[Products]/[Reactants]}
Χ.∆G’ = ∆ Go’+ RTln {[reactants]/[Products]}
∆.∆Go’ = ∆ G’+ RTln {[Products]/[Reactants]}
Ε.∆G’ = ∆ Go’+ RT {[Products]/[Reactants]}
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17. Practice questions
15.Concider the reaction A  B  C  D ,if A  B if
unfavorable with +5 kcal/mol and C  D is
favorable, -8 kcal/mol
A.The reaction forward is driven by +3 kcal/mol
B.The reaction forward is driven by- 11kcal/mol
C.The reaction forward is driven by -8 kcal/mol
D.The reaction forward is driven by -3 kcal/mol
E.Cannot tell from this information
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18. Practice questions
16. To have a favorable thermodynamic process
which of the following is /are
A.The ∆H is negative
B.The ∆ S is positive, randomness increases
C.The ∆ G < 0
D.The reaction must be exothermic or exergonic
E.All of the above
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19. Practice questions
17.If a reaction is spontaneous, it will have
A.A negative Eo, negative delta G, and a large K
B. A positive Eo, negative delta G, and a large K
C. A positive Eo, negative delta G, and a small K
D.A positive Eo positive delta G, and a large K
E. A negative Eo, negative delta G, and a small K
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20. Practice questions
18. What is NOT supportive for the chemiosmotic
hypothesis
A.A proton-motive force responsible for driving the synthesis
of ATP.
B. Protons would be pumped across the inner mitochondrial
membrane as electrons went through the electron transfer
chain.
C. Aproton gradient with high pH in the intermembrane space
and low pH in the matrix of the mitochondria.
D.An intact inner mitochondrial membrane, impermeable to
protons, is a requirement of such a model
E. C and D
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21. Practice questions
19.New born and hibernating animals contain brown
fat. Brown fat mitochondria contain
---------------------which provides a channel through
the inner mitochondrial membrane.
A.Cytochrome oxidase
B.Thermogenin
C.Proton permeable inner mitochondrial membrane
D.Many iron sulfur complexes
E.Inhibitors of electron flow
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22. 20.Calculate the energy obtained from
oxidation of NADH
Transfer of 2 electrons from NADH to oxygen:
• a. ½O2 + 2H+
+ 2 e-
 H2O E°' = + 0.815 V b. NAD+
+ 2H+
+ 2 e-
NADH + H+
E°' = - 0.315 V
• Subtracting reaction b from reaction a: ½O2 +
NADH + H+
 H2O + NAD+
∆ E°' = + 1.13 V
• ∆G ' = - nF∆Eo
' = - 2(96485 Joules/Volt · mol)
(1.13 V) = - 218 kJ/
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23. Practice questions
21.If a reaction is at equilibrium, the free energy
change (∆G ) is
A. Equal to -RT x lnKeq
B. Equal to the concentrations of the substrate and
product
C. Equal to the ∆G under standard conditions
D. Equal to zero
E. equal to the change in entropy
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24. 20.Calculate the energy obtained from
oxidation of NADH
Transfer of 2 electrons from NADH to oxygen:
• a. ½O2 + 2H+
+ 2 e-
 H2O E°' = + 0.815 V b. NAD+
+ 2H+
+ 2 e-
NADH + H+
E°' = - 0.315 V
• Subtracting reaction b from reaction a: ½O2 +
NADH + H+
 H2O + NAD+
∆ E°' = + 1.13 V
• ∆G ' = - nF∆Eo
' = - 2(96485 Joules/Volt · mol)
(1.13 V) = - 218 kJ/
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25. Practice questions
22. The chemiosmotic hypothesis for oxidative phosphorylation
proposes that the mechanism for the formation of ATP involves
A. a change in the hydrogen bonds and hydrophobic bonds between
proteins within the mitochondrial membrane.
B. the joining of protons and oxygen to form water.
C. the formation of a high energy bond between Pi and a protein in the
mitochondrial membrane.
D. the pumping of water through the mitochondrial membrane.
E. the flow of protons through ATP synthase in the mitochondrial
membrane.
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26. Practice questions
23. Which of the following cofactors are
required during the reduction of coenzyme Q
with electrons from complex II?
A. FAD
B. Copper
C. Iron-Porphyrin
D. Cytochrome a
E. FMN
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27. Practice questions
22. The chemiosmotic hypothesis for oxidative phosphorylation
proposes that the mechanism for the formation of ATP involves
A. a change in the hydrogen bonds and hydrophobic bonds between
proteins within the mitochondrial membrane.
B. the joining of protons and oxygen to form water.
C. the formation of a high energy bond between Pi and a protein in the
mitochondrial membrane.
D. the pumping of water through the mitochondrial membrane.
E. the flow of protons through ATP synthase in the mitochondrial
membrane.
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28. Practice questions
23. Which of the following cofactors are
required during the reduction of coenzyme Q
with electrons from complex II?
A. FAD
B. Copper
C. Iron-Porphyrin
D. Cytochrome a
E. FMN
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29. Practice questions
24.The standard reduction potential for a
reaction
A. is unrelated to the free energy of the
reaction.
B. changes in the presence of oxygen.
C. is negative for a spontaneous process.
D. is an oxidation potential.
E. measures the tendency to donate electrons.
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30. Practice questions
25. Uncoupling of oxidative phosphorylation
A. decreases the oxygen flow to the tissues.
B. releases heat.
C. occurs during hypoxia.
D. prevents overproduction of ATP.
E. is most easily accomplished with electron
transport blockers.
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31. Practice questions
26. The mitochondrial respiratory chain (electron
transport chain) transfers electrons to molecular
oxygen to produce water. If cyanide were added,
the cytochromes would
A. become more reduced.
B. become less reduced.
C. be unchanged.
D. become uncoupled.
E. consume ATP.
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32. Practice questions
27. When dinitrophenol is added to mitochondria, it
A. decreases the flow of electrons through
cytochrome oxidase.
B. results in an increase in the intramitochondrial
ratio of ATP/ADP.
C. uncouples oxidative phosphorylation.
D. increases the rate of ATP formation.
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