Practice QuestionsBioenergeticsDr T.NyamboDepartment of BiochemistrySchool of MedicineMUHAS4 December 2016

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

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Practice questionsThe standard free energy 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 + PyrophosphateA.-0.5 kcal/moleB.-7.8 kcal/moleC.-15.1 kcal/moleD.+0.5 kcal/moleE.+15.1 kcal/mole*

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Practice questions1.The free energy of hydrolysis of a compound must be at least ________, in order for it to be considered a "high-energy" compound.-3 kcal/mol-5 kcal/mol-7 kcal/mol-9 kcal/mol*

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Practice questions2.The standard free energy (DG') of ATP hydrolysis to ADP + Pi is about+30 kJ/mol.+14 kJ/mol-14 kJ/mol-30 kJ/mol-62 kJ/mol.*

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Practice questions3. 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-0.5 kcal/mole-7.8 kcal/mole-15.1 kcal/mole+0.5 kcal/mole+15.1 kcal/mole*

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Practice questions4. High energy compounds include all of the following EXCEPT:EstersPhosphate anhydridesEnol phosphates (phosphoenol pyruvate)ThioestersCreatine phosphate*

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Practice questions5.Glucose 1-phosphate can be converted to fructose 6-phosphate in the following two reactions. The value Go for the overall conversion is:Glucose 1-phosphate glucose 6-phosphate Go = -7.1kJ/molGlucose 6-phosphate fructose 6-phosphate Go = -1.7kJ/mol+5.5kJ/mol +8.8 kJ/mol8.8kJ/mol 5.5kJl/mol-0.0 kJ/mol

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Practice questions6. Coupled reactions involved in the trapping of free energy from fuel molecules consist ofTwo endergonic reactions, one of which has a higher standard free energy change (Go') than the other Two exergonic reactions, one of which has a lower Go' than the otherOne exergonic reaction coupled to an endergonic reaction, which has a lower Go' than the exergonic reactionOne endergonic reaction coupled to an exergonic reaction, which has a lower Go' than the endergonic reactionNone of the above*

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Practice questions7.What part of the electron transport chain does cyanide (CN-) react with?Complex IComplex IIComplex IIIComplex IVCytochrome C*

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Practice questions9. 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 c1B.Cytochrome oxidaseC.Cytochrome cD.Coenzyme QE.Cytochrome b*

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Practice questions10. 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?The actual free energy of hydrolysis of ATP is only -11 to -12 kcal.ATP is not located in the cytoplasm where most endergonic reactions occur.The half-life of ATP is too short.The synthesis rate for ATP is not efficient.None of the above *

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Practice questions11.What is the value of Go' for the pathway A B C D?Reaction Go'B A +20 kJ/molC A +20 kJ/molC D -60kJ/molA. +40B. +20C. -40D. -60E. 80*

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Practice questions12. 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 glucose 6-phosphate Go = -1.7 kcal/molGlucose 6-phosphate fructose 6-phosphate Go = -0.4 kcal/mol-2.1 kcal/mol-1.3 kcal/mol-0.0 kcal/mol+1.3 kcal/mol+2.1 kcal/mol*

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Practice Questions13. In the electron transport scheme below, which electron carrier is missing?NADH FMNH2?? cytochromes O2

Vitamin KVitamin CFerridoxinUbiquinone (coenzyme Q)NADPH*

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Practice questions 14.The actual free energy change (G for a reaction is equal to G = Go+ RTlog10 {[Products]/[Reactants]}G = Go+ RTln {[Products]/[Reactants]}G = Go+ RTln {[reactants]/[Products]}Go = G+ RTln {[Products]/[Reactants]}G = Go+ RT {[Products]/[Reactants]}*

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Practice questions15.Concider the reaction A B C D ,if A B if unfavorable with +5 kcal/mol and C D is favorable, -8 kcal/mol The reaction forward is driven by +3 kcal/molThe reaction forward is driven by- 11kcal/molThe reaction forward is driven by -8 kcal/molThe reaction forward is driven by -3 kcal/molCannot tell from this information*

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Practice questions 16. To have a favorable thermodynamic process which of the following is /areThe H is negativeThe S is positive, randomness increases The G < 0 The reaction must be exothermic or exergonic All of the above*

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Practice questions 17.If a reaction is spontaneous, it will have A negative Eo, negative delta G, and a large K A positive Eo, negative delta G, and a large K A positive Eo, negative delta G, and a small K A positive Eo positive delta G, and a large K A negative Eo, negative delta G, and a small K *

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Practice questions

18. What is NOT supportive for the chemiosmotic hypothesis A proton-motive force responsible for driving the synthesis of ATP. Protons would be pumped across the inner mitochondrial membrane as electrons went through the electron transfer chain. Aproton gradient with high pH in the intermembrane space and low pH in the matrix of the mitochondria.An intact inner mitochondrial membrane, impermeable to protons, is a requirement of such a modelC and D*

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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 oxidaseB.ThermogeninC.Proton permeable inner mitochondrial membraneD.Many iron sulfur complexesE.Inhibitors of electron flow*

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20.Calculate the energy obtained from oxidation of NADHTransfer of 2 electrons from NADH to oxygen:a. O2 + 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: O2 + NADH + H+ H2O + NAD+ E' = + 1.13 V G ' = - nFEo' = - 2(96485 Joules/Volt mol)(1.13 V) = - 218 kJ/

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Practice questions 21.If a reaction is at equilibrium, the free energy change (G ) isA. Equal to -RT x lnKeqB. Equal to the concentrations of the substrate and productC. Equal to the G under standard conditionsD. Equal to zeroE. equal to the change in entropy *

20.Calculate the energy obtained from oxidation of NADHTransfer of 2 electrons from NADH to oxygen:a. O2 + 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: O2 + NADH + H+ H2O + NAD+ E' = + 1.13 V G ' = - nFEo' = - 2(96485 Joules/Volt mol)(1.13 V) = - 218 kJ/

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Practice questions22. The chemiosmotic hypothesis for oxidative phosphorylation proposes that the mechanism for the formation of ATP involvesA. 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.*

Practice questions23. Which of the following cofactors are required during the reduction of coenzyme Q with electrons from complex II?A. FADB. CopperC. Iron-PorphyrinD. Cytochrome aE. FMN*

Practice questions22. The chemiosmotic hypothesis for oxidative phosphorylation proposes that the mechanism for the formation of ATP involvesA. 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.*

Practice questions23. Which of the following cofactors are required during the reduction of coenzyme Q with electrons from complex II?A. FADB. CopperC. Iron-PorphyrinD. Cytochrome aE. FMN*

Practice questions 24.The standard reduction potential for a reactionA. 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.*

Practice questions 25. Uncoupling of oxidative phosphorylationA. 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.*

Practice questions26. 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.*

Practice questions27. When dinitrophenol is added to mitochondria, itA. 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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