exam 2
For every two electrons transferred from NADH to oxygen, _____ protons are pumped from the matrix to the intermembrane space.
10
How many protons are moved across the inner mitochondrial membrane at Complex III?
4
2,4-Dinitrophenol (DNP) and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4-Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself.Therefore, 2,4-dinitrophenol will: A. allow electron transfer in the presence of oligomycin. B. allow oxidative phosphorylation in the presence of oligomycin. C. block electron transfer in the presence of oligomycin. D. diminish O2 consumption in the presence of oligomycin
A
2,4-Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4- Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4-dinitrophenol will: A) allow electron transfer in the presence of oligomycin. B) allow oxidative phosphorylation in the presence of oligomycin. C) block electron transfer in the presence of oligomycin. D) diminish O2 consumption in the presence of oligomycin. E) None of the answers is correct.
A
Complex III contains which cofactor as a prosthetic group? A) iron-sulfur clusters B) FAD C) FMN D) coenzyme Q E) copper
A
Cytochrome c oxidase contains four redox centers, which include two ______ atoms which areunique to this complex. A. Cu B. Ca C. Fe D. S
A
Electron flow down the electron-transport chain leads to the A. transport of protons across the inner mitochondrial membrane from inside the matrix tothe intermembrane space. B. transport of protons across the inner mitochondrial membrane from the intermembranespace into the matrix. C. coupled synthesis of GTP. D. a dangerous imbalance of K+ ions across the mitochondiral membrane.
A
If electron transfer in tightly coupled mitochondria is blocked (with antimycin A) between cytochrome b and cytochrome c1, then: A) all ATP synthesis will stop. B) ATP synthesis will continue, but the P/O ratio will drop to one. C) electron transfer from NADH will cease, but O2 uptake will continue. D) electron transfer from succinate to O2 will continue unabated. E) energy diverted from the cytochromes will be used to make ATP, and the P/O ratio will rise.
A
In photophosphorylation, absorption of light energy in chloroplast "light reactions" leads to: A) absorption of CO2 and release of O2. B) absorption of O2 and release of CO2. C) hydrolysis of ATP and reduction of NADP+. D) synthesis of ATP and oxidation of NADPH. E) use of iron-sulfur proteins.
A
In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2 because: A) cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor. B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor. C) cytochrome c is water soluble and operates between the inner and outer mitochondrial membranes D) heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much cytochrome c as QH2 for electron transfer to proceed normally. E) two molecules of cytochrome c must first combine physically before they are catalytically active.
A
Oxidative phosphorylation and photophosphorylation share all of the following except: A) chlorophyll. B) involvement of cytochromes. C) participation of quinones. D) proton pumping across a membrane to create electrochemical potential. E) use of iron-sulfur proteins.
A
Rotenone inhibits electron transport at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
A
Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate, what does NOT occur? A) Oxygen consumption decreases. B) Oxygen consumption increases. C) The P/O ratio drops from a value of approximately 2.5 to 0. D) The proton gradient dissipates. E) The rate of transport of electrons from NADH to O2 becomes maximal.
A
What is the immediate result of the reaction catalyzed by superoxide dismutase? A. Conversion of the free radical O2-to H2O2. B. Conversion of the free radical O2-to H2O. C. Conversion of the free radical O2-to CO2. D. Conversion of the free radical O2-to CO.
A
What will NOT occur when 2,4-dinitrophenol (an uncoupler of oxidative phosphorylation) is added to actively respiring mitochondria? A) The P:O ratio will increase. B) The rate of NADH reoxidation at Complex I will increase. C) The rate of oxidation of intermediates in the citric acid cycle will increase. D) Proton export from the matrix will occur. E) Heat will be released.
A
Which cofactor is MOST commonly involved as a cosubstrate in catabolic reactions where a metabolite is oxidized? A) NAD+ B) FAD C) NADPH D) NADH E) coenzyme Q
A
Which of the following electron carriers is NOT able to transfer one electron at a time? A) NADH B) FMN C) FAD D) ubiquinone E) heme
A
Which of the following statements about the chemiosmotic theory is correct? A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on oneside of the inner mitochondrial membrane. B) It predicts that oxidative phosphorylation can occur even in the absence of an intact innermitochondrial membrance. C) The effect of uncoupling reagents is a consequence of their ability to carry electrons throughmembranes. D) The membrane ATP synthase has no significant role in the chemiosmotic theory. E) All of the above are correct.
A
Which of the following statements about the mitochondrial inner membrane is FALSE? A. The inner membrane is permeable to CO2, H2O, and small ions. B. The inner membrane contains about 75% protein. C. The inner membrane contains many respiratory proteins. D. The inner membrane is highly invaginated.
A
Which one of the following is true about reaction centers? A) Cyanobacteria and plants have two reaction centers arranged in tandem. B) Cyanobacteria contain a single reaction center of the Fe-S type. C) Green sulfur bacteria have two reaction centers arranged in tandem. D) Plant photosystems have a single reaction center of the pheophytin-quinone type. E) Purple bacteria contain a single reaction center of the Fe-S type.
A
Which one of the following statements about human mitochondria is true? A) About 900 mitochondrial proteins are encoded by nuclear genes. B) Mitochondrial genes are inherited from both maternal and paternal sources. C) rRNA and tRNA are imported from the cytoplasm and used in mitochondrial protein synthesis. D) The mitochondrial genome codes for all proteins found in mitochondria. E) The mitochondrial genome is not subject to mutations.
A
Which statement about human mitochondria is TRUE? A) About 900 mitochondrial proteins are encoded by nuclear genes. B) Mitochondrial genes are inherited from both maternal and paternal sources. C) rRNA and tRNA are imported from the cytoplasm and used in mitochondrial protein synthesis. D) The mitochondrial genome codes for all proteins found in mitochondria. E) The mitochondrial genome is not subject to mutations.
A
Which statement about the chemiosmotic theory is CORRECT? A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. B) It predicts that oxidative phosphorylation can occur, even in the absence of an intact inner mitochondrial membrance. C) The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes. D) The membrane ATP synthase has no significant role in the chemiosmotic theory. E) All of the statements are correct.
A
Which statement is NOT true of electron transport? A) The mobile electron carrier coenzyme A is located in the inner mitochondrial membrane. B) Electrons flow from redox centers with a lower reduction potential to redox centers with a higher reduction potential. C) The electron transport chain oxidizes reduced cofactors. D) Cytochrome C has a higher reduction potential than FADH2. E) None of the statements is true.
A
Which statement is TRUE regarding the gamma (γ) subunit of ATP synthase? A) It contains mostly α-helical regular secondary structure. B) It exists as a dimer in the F1 portion of ATP synthase. C) It prevents the F1 portion from rotating relative to the FO portion. D) It interacts with the a and b subunits of the FO portion. E) It binds protons as part of the proton translocation process.
A
Choose the correct path taken by a pair of electrons as it travels down the electron-transportchain. A. NADH → complex I → CoQ → Complex III → Cyt c → complex IV → O2 B. FADH2 → complex I → CoQ → Complex III → Cyt c → complex IV → O2 C. NADH → complex I → complex II→ Complex III → Cyt c → complex IV → O2 D. FADH2 → complex II → CoQ → Complex III → Cyt c → complex IV → O2 E. a and d
A, D, E
Isolated mitochondria are suspended in a medium containing succinate. The graph shows oxygen consumed (solid line) and ATP synthesized (dotted line) over time in the mitochondria following the addition of various substances. What is most likely added at time 1?
ADP + Pi
Antimycin A blocks electron transfer between cytochromes b and c1. If intact mitochondria were incubated with antimycin A, excess NADH, and an adequate supply of O2, which compound would be found in the oxidized state? A) coenzyme Q B) cytochrome a3 C) cytochrome b D) cytochrome e E) cytochrome f
B
Complexes I and II each transfer electrons to A. NAD+ B. CoQ C. Cytochrome C D. O2
B
Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial oxidativephosphorylation. Which of the following statements correctly describes the mode of action of thethree inhibitors? A. Cyanide and 2,4-dinitrophenol inhibit the respiratory chain, and oligomycin inhibits thesynthesis of ATP. B. Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit thesynthesis of ATP. C. Cyanide, oligomycin, and 2,4-dinitrophenol compete with O2 for cytochrome oxidase (ComplexIV). D. Oligomycin and cyanide inhibit synthesis of ATP; 2,4-dinitrophenol inhibits the respiratorychain. E. Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4-dinitrophenol prevent thesynthesis of ATP
B
Cyclic electron flow in chloroplasts produces: A) ATP and O2, but not NADPH. B) ATP, but not NADPH or O2 . C) NADPH, and ATP, but not O2 . D) NADPH, but not ATP or O2 . E) O2, but not ATP or NADPH.
B
During the operation of the malate-aspartate shuttle, what process does NOT occur? A) net movement of reducing potential from the cytosol to the matrix B) transfer of amino groups from glutamate to oxaloacetate in the cytosol C) transport of two different amino acids through an antiport D) simultaneous transport of malate and oxaloacetate through an antiport E) reduction of oxaloacetate to malate in the cytosol
B
In some organisms, an alternative oxidase will accept electrons from ubiquinol and reduce oxygen to water with no associated proton translocation. What would be a consequence of having this oxidase active? A) decreased rate of NADH reoxidation B) decreased P:O ratio C) decreased rate of oxygen consumption D) inhibition of oxidative pathways like the citric acid cycle E) increased sensitivity to cyanide poisoning
B
Mammals produce heat by using which endogenous uncoupling agent? A) the small molecule 2-4-dinitrophenol synthesized by the cell B) the protein thermogenin C) the protein thioredoxin D) the protein cytochrome c E) a modified form of the FoF1 ATPase
B
Mutations in mitochondrial genes do NOT play a role in: A) adult onset diabetes. B) cystic fibrosis. C) hypertrophic cardiomyopathy. D) Leber's hereditary optic neuropathy. E) myoclonic epilepsy.
B
Mutations in mitochondrial genes play a role in each of the following diseases except: A) adult onset diabetes. B) cystic fibrosis. C) hypertrophic cardiomyopathy. D) Leber's hereditary optic neuropathy. E) myoclonic epilepsy.
B
New born babies produce heat by using the endogenous uncoupling agent: A. the small molecule 2-4-Dinitrophenol synthesized by the cell. B. the protein thermogenin. C. the protein thioredoxin. D. the protein cytochrome c. E. a modified form of the F0F1 ATPase.
B
Several prosthetic groups act as redox centers in Complex I, including A. FMN, ubiquinone, iron-sulfur clusters, heme. B. FMN, ubiquinone, iron-sulfur clusters. C. heme, ubiquinone, iron-sulfur clusters. D. all of the above E. none of the above
B
The electrons formed from the oxidation of glucose are A. directly transferred to O2 during the citric acid cycle. B. transferred to the coenzymes NAD+ and FAD. C. transferred to succinate and arachidonic acid. D. A and B E. none of the above
B
The experimental determination of the effectiveness of light of different colors in promotingphotosynthesis is called the: A) absorption spectrum. B) action spectrum. C) difference spectrum. D) reflectance spectrum. E) refraction spectrum.
B
What compound is a product of the reaction involving the superoxide free radical catalyzed by superoxide dismutase? A) water B) hydrogen peroxide C) reduced glutathione D) oxidized glutathione E) NADPH
B
What product of glycolysis is transported into the mitochondria? A. Acetate as acetyl CoA B. Pyruvate C. Ethanol D. Lactic acid
B
Which complex is unable to generate sufficient free energy to power ATP synthesis? A. Complex I B. Complex II C. Complex III D. Complex IV E. All the complexes are able to generate sufficient free energy.
B
Which component of the electron-transport chain is NOT an integral membrane protein? A) NADH dehydrogenase B) cytochrome c C) cytochrome oxidase D) ubiquinone:cytochrome c oxidoreductase E) succinate dehydrogenase
B
Which of the following statements about the light reactions in photosynthetic plants is false? A) A membrane-bound ATPase couples ATP synthesis to electron transfer. B) No CO2 is fixed in the light reactions. C) The ultimate electron acceptor is O2. D) The ultimate source of electrons for the process is H2O. E) There are two distinct photosystems, linked together by an electron transfer chain.
B
Which statement does NOT describe a difference between the inner and outer mitochondrial membranes? A) The outer mitochondrial membrane contains porins, whereas the inner mitochondrial membrane does not. B) The outer mitochondrial membrane is permeable to large proteins (Mr > 10,000), whereas the inner mitochondrial membrane is not. C) A pH gradient exists across the inner mitochondrial membrane but not the outer mitochondrial membrane. D) The inner mitochondrial membrane contains a smaller percentage of lipid relative to protein compared with the outer mitochondrial membrane. E) The outer mitochondrial membrane has a smaller surface area than the inner mitochondrial membrane.
B
Which statement explains why the [ATP]/[ADP][Pi] ratio is relatively stable in a cell? A) [ATP] is always relatively low. B) ATP consumption is balanced by ATP synthase activity. C) ATP is used to regulate protein kinases. D) ATPases ensure that ATP concentration does not become too large. E) Energy consumption is minimized to ensure ATP is not consumed.
B
Coenzyme Q carries electrons from complex _______ to complex _______. A. I; II B. II; III C. I; III D. III; IV
B, C
Which statement concerning Complex II of the electron transport chain is false? A. This complex oxidizes FADH2 and reduces coenzyme Q. B. This complex includes a cytochrome heme. C. This complex includes Fe-S centers. D. This complex pumps protons from the matrix to the intermembrane space. E. This complex also oxidizes succinate to fumarate in the TCA cycle.
B, D
The infoldings of the inner mitochondrial membrane are called A. cisternae. B. cristae. C. laminae. D. lacunae.
B. cristae.
Cytochrome P-450 gets its name from what characteristic? A) It is a protein that is 450 amino acids long. B) It fluoresces at 450 nm. C) It absorbs light at 450 nm. D) It has a reduction potential of ñ450 mV. E) It contains a 450 Dalton prosthetic group.
C
Cytochrome c can be reduced directly by small molecules such as ascorbate (vitamin C). If ascorbate is added to an oxygenated solution containing purified cytochrome c and cytochrome oxidase, what would you predict would occur? A) ATP synthesis would occur. B) Cytochrome c would become reduced and remain reduced. C) Oxygen would be reduced to water. D) Ascorbate would become more reduced. E) No apparent change would be observed.
C
During oxidative phosphorylation, the proton motive force (electrochemical gradient) that is generated by electron transport is used to: A) create a pore in the inner mitochondrial membrane. B) generate the substrates (ADP and Pi) for ATP synthase. C) drive transport processes essential to oxidative phosphorylation. D) reduce NAD+ to NADH. E) reduce O2 to H2O.
C
During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to: A) create a pore in the inner mitochondrial membrane. B) generate the substrates (ADP and Pi) for the ATP synthase. C) induce a conformational change in the ATP synthase. D) oxidize NADH to NAD+ . E) reduce O2 to H2O.
C
Electron transport and oxidative phosphorylation are performed by protein complexesin the mitochondrial A. outer membrane. B. intermembrane space. C. inner membrane. D. matrix
C
How many molecules of water are produced by the electron-transport chain during the complete aerobic oxidation of one molecule of pyruvate? A) 3 H2O B) 4 H2O C) 5 H2O D) 8 H2O E) 10 H2O
C
If a drug that specifically prevented the interaction of cytochrome c with other proteins was added to respiring mitochondria in a test tube, what effects would be observed? A) ATP synthesis would immediately stop. B) Oxygen consumption would increase. C) Reduced cofactors (NADH/FADH2) would accumulate. D) Coenzyme Q would become oxidized. E) Proton export from the matrix would increase.
C
In the photolytic cleavage of water by the oxygen-evolving complex [2H2O → 4 H+ + 4e- + O2], howmany photons of light at a wavelength of 680 nm are required? A) 1 B) 2 C) 4 D) 6 E) 8
C
In what order do the following five steps occur in the photochemical reaction centers? 1) Excitation of the chlorophyll a molecule at the reaction center 2) Replacement of the electron in the reaction center chlorophyll 3) Light excitation of antenna chlorophyll molecule 4) Passage of excited electron to electron-transfer chain 5) Exiton transfer to neighboring chlorophyll A) 1-2-3-4-5 B) 3-2-5-4-1 C) 3-5-1-4-2 D) 4-2-3-5-1 E) 5-4-3-2-1
C
Most small molecules are permeable across A. both mitochondrial membranes. B. the inner, but not the outer, mitochondrial membrane. C. the outer, but not the inner, mitochondrial membrane. D. neither mitochondrial membrane
C
Photosynthetic phosphorylation and oxidative phosphorylation appear to be generally similarprocesses, both consisting of ATP synthesis coupled to the transfer of electrons along an electroncarrier chain. Which of the following is not true of both processes? A) Both contain cytochromes and flavins in their electron carrier chains. B) Both processes are associated with membranous elements of the cell. C) Both use oxygen as a terminal electron acceptor. D) Each represents the major route of ATP synthesis in those cells in which it is found. E) Protons are pumped from the inside to the outside of both mitochondria and chloroplastmembranes
C
Reduced QH2 is NOT formed by which of the following? A) Complex I and NADH B) Complex II and succinate C) Complex III and cytochrome c D) fatty acid oxidation E) oxidation of glycerol-3-phosphate
C
The cytochromes contain _____ groups. A. NAD+ B. CoQ C. heme D. Fe-S centers
C
The oxidation of a particular hydroxy substrate to a keto product by mitochondria has a P/O ratio of less than 2. The initial oxidation step is very likely directly coupled to the: A) oxidation of a flavoprotein. B) oxidation of a pyridine nucleotide. C) reduction of a flavoprotein. D) reduction of a pyridine nucleotide. E) reduction of cytochrome a3.
C
Uncoupling of mitochondrial oxidative phosphorylation: A) allows continued mitochondrial ATP formation but halts O2 consumption. B) halts all mitochondrial metabolism. C) halts mitochondrial ATP formation but allows continued O2 consumption. D) slows down the citric acid cycle. E) slows the conversion of glucose to pyruvate by glycolysis.
C
What factor makes the outer mitochondrial membrane permeable to protons? A) proton symports B) proton antiports C) porins D) the presence of proton ionophores E) the presence of negatively charged lipids
C
What is the chemical effect of oligomycin on aerobic metabolism? A. The flow of electrons from NADH to CoQ is blocked. B. The flow of electrons from Cyt c to oxygen is blocked. C. Oligomycin blocks the proton transfer through Fo of ATP synthase and therefore blocksthe phosphorylation of ADP to form ATP. D. The transport of ATP out of and ADP into the mitochondria is blocked. E. Oxidative phosphorylation is uncoupled from electron transport and all the energy is lostas heat.
C
Which of the following statements about energy conservation in the mitochondrion is false? A. Drug that inhibits the ATP synthase will also inhibit the flow of electrons down the chain ofcarriers. B. For oxidative phosphorylation to occur, it is essential to have a closed membranous structurewith an inside and an outside. C. Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitorssuch as cyanide; both block further electron transfer to oxygen. D. Uncouplers "short circuit" the proton gradient, thereby dissipating the proton motive force asheat
C
Which one of the following statements about photophosphorylation is false? A) It can be uncoupled from electron flow by agents that dissipate the proton gradient. B) The difference in pH between the luminal and stromal side of the thylakoid membrane is 3 pHunits. C) The luminal side of the thylakoid membrane has a higher pH than the stromal side. D) The number of ATPs formed per oxygen molecule is about three. E) The reaction centers, electron carriers, and ATP-forming enzymes are located in the thylakoidmembrane.
C
Which protein associated with electron transport below is NOT a flavoprotein? A) NADH dehydrogenase B) mitochondrial glycerol-3-phosphate dehydrogenase C) cytochrome oxidase D) succinate dehydrogenase E) acyl-CoA dehydrogenase
C
Which statement does NOT describe characteristics of the protein inhibitor IF1? A) This protein is relatively small (<100 amino acids). B) This protein has very little ordered structure at pH 7.0. C) This protein will bind to the FO portion of ATP synthase. D) This protein functions as a dimer when it is inhibiting ATP synthesis. E) This protein inhibits ATP hydrolysis by ATP synthase.
C
Which statement is NOT true of the proton motive force (pmf)? A) One component of the pmf is the chemical gradient of protons. B) One component of the pmf is the charge gradient of protons. C) Generation of the pmf in mitochondria requires succinate. D) The pmf is generated by the electron transport chain in mitochondria. E) The pmf drives ATP synthesis in mitochondria.
C
Which statement is TRUE regarding the reduction potential of mitochondrial glycerol 3 phosphate dehydrogenase? A) It will be higher than those of both NADH and Complex III. B) It will be lower than those of both NADH and Complex III. C) It will be higher than that of NADH but lower than that of Complex III. D) It will be lower than that of NADH but higher than that of Complex III. E) No conclusion can be drawn regarding its reduction potential.
C
Which statement regarding oxidative phosphorylation is TRUE? A) The rate of electron transport is independent of the magnitude of the proton electrochemical gradient. B) ATP synthase utilizes oxidized cofactors. C) Proton transfer through the Fo subunit of ATP synthase is required in order for ATP synthesis to occur. D) The addition of an uncoupler decreases the rate of re-oxidation of NADH and FADH2, therefore decreasing the rate of the citric acid cycle. E) All of the statements are true.
C
Almost all of the oxygen (O2) one consumes in breathing is converted to: A) acetyl-CoA. B) carbon dioxide (CO2). C) carbon monoxide and then to carbon dioxide. D) water. E) None of the answers is correct.
D
Cyanide inhibits electron transport at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
D
For mitochondria where an uncoupler for oxidative phosphorylation is present, which statement is TRUE? A) The rate of NADH reoxidation will decrease relative to coupled mitochondria. B) The citric acid cycle will be inhibited relative to uncoupled mitochondria. C) The P:O ratio for FADH2 will increase relative to uncoupled mitochondria. D) The amount of ATP generated from FADH2 will be less than the amount of ATP generated from NADH. E) None of the statements is true.
D
How many ATP molecules are synthesized from the oxidation of 1 NADH molecule? A. 1 B. 1.5 C. 2 D. 2.5 E. 3
D
How many of cytochrome c need to be reoxidized for every oxygen molecule (O2) converted to water? A) one B) two C) three D) four E) eight
D
In which pairing are both transporters symports? A) adenine nucleotide translocase and phosphate translocase B) phosphate translocase and pyruvate translocase C) pyruvate translocase and adenine nucleotide translocase D) adenine nucleotide translocase and glutamate-aspartate transporter E) glutamate-aspartate transporter and phosphate translocase
D
Newborns generate heat by nonshivering thermogenesis that occurs in ______ tissue. A. muscle B. liver C. pancreatic D. brown adipose (fat) E. white adipose tissue
D
Oxidative phosphorylation is regulated by A. the availability of reduced cofactors from catabolic pathways. B. the availability of the dNTPs. C. the availability of ADP and Pi. D. A and C E. A, B, and C
D
The consumption of acetyl-CoA by the citric acid cycle is DECREASED under which condition? A) the concentration of NAD+ being high B) the concentration of oxaloacetate being high C) NADH being rapidly re-oxidized via the electron-transport chain D) the mitochondrial ATP synthase being inactive E) the concentration of both NAD+ and oxaloacetate being high
D
The inner compartment of mitochondria is called the A. stroma. B. intermembrane space C. inner membrane space. D. matrix
D
The inner mitochondrial membrane contains proteins that A. synthesize ATP. B. pump protons. C. transport pyruvate and fatty acids. D. All of the above
D
The light reactions in photosynthetic higher plants: A) do not require chlorophyll. B) produce ATP and consume NADH. C) require the action of a single reaction center. D) result in the splitting of H2O, yielding O2. E) serve to produce light so that plants can see underground.
D
The rate of oxidative phosphorylation in mitochondria is controlled primarily by: A) feedback inhibition by CO2. B) the availability of NADH from the TCA cycle. C) the concentration of citrate (or) the glycerol-3-phosphate shuttle. D) the mass-action ratio of the ATD-ADP system. E) the presence of thermogenin.
D
What effect will increasing the number of c subunits in ATP synthase have on the P:O ratio? A) It will increase for both NADH and FADH2. B) It will increase for NADH and decrease for FADH2. C) It will decrease for NADH and increase for FADH2. D) It will decrease for both NADH and FADH2. E) It will remain unchanged for both NADH and FADH2.
D
What is the P:O ratio for electrons entering the electron-transport chain that originate from reoxidation of acyl-CoA dehydrogenase? A) greater than the P:O ratio for NADH reoxidation B) approximately the same as the P:O ratio for NADH reoxidation C) less than the P:O ratio for NADH reoxidation but more than the P:O ratio for Complex II reoxidation D) approximately the same as the P:O ratio for Complex II reoxidation E) less than the P:O ratio for Complex II reoxidation
D
What is the role of cytochrome c in apoptosis? A) It acts as an allosteric effector for caspase-3. B) It transports electrons from mitochondria to the cytosol. C) It acts as a protease to activate various zymogens. D) It forms a complex with other proteins to generate an apoptosome. E) It activates pores in the outer mitochondrial membrane.
D
What mechanism accounts for mitochondrial inheritance in sexual reproduction in animals? A) Male gametes do not contain mitochondria. B) Mitochondria from male gametes do not enter the ovum. C) Female mitochondria are able to outcompete male mitochondria. D) Male mitochondria are degraded after fertilization. E) Male and female mitochondria merge after fertilization to form hybrids.
D
What type of gradient is critical to ATP formation by oxidative phosphorylation? A. sodium ion B. potassium ion C. chloride ion D. proton
D
When the ΔG'° of the ATP synthesis reaction is measured on the surface of the ATP synthaseenzyme, it is found to be close to zero. This is thought to be due to: A) a very low energy of activation. B) enzyme-induced oxygen exchange. C) stabilization of ADP relative to ATP by enzyme binding. D) stabilization of ATP relative to ADP by enzyme binding. E) none of the above.
D
When the ΔG'∞ of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it is found to be close to zero. This is thought to be due to: A) a very low energy of activation. B) enzyme-induced oxygen exchange. C) stabilization of ADP relative to ATP by enzyme binding. D) stabilization of ATP relative to ADP by enzyme binding. E) None of the answers is correct.
D
Which characteristic describes heme a but not heme c? A) noncovalently associated prosthetic group B) contains an isoprenoid structure C) contains an aldehyde substituent on the porphyrin ring D) contains two propionate substituents on the porphyrin ring E) contains a vinyl substituent on the porphyrin ring
D
Which complex in the electron-transport chain contains copper ions? A) Complex I B) Complex II C) Complex III D) Complex IV E) None of these complexes contains copper ions.
D
Which factor is NOT controlled by hypoxia-inducible factor (HIF-1)? A) glucose transport B) glycolysis C) citric acid cycle D) Compex I of the respiratory chain E) Complex IV of the respiratory chain
D
Which list shows the proteins in the CORRECT order from highest to lowest reduction potential? A) acyl-CoA dehydrogenase → ETF:Q oxidoreductase → ETF B) ETF → ETF:Q oxidoreductase → acyl-CoA dehydrogenase C) ETF:Q oxidoreductase → acyl-CoA dehydrogenase → ETF D) ETF:Q oxidoreductase → ETF → acyl-CoA dehydrogenase E) ETF → acyl-CoA dehydrogenase → ETF:Q oxidoreductase
D
Which molecule can reduce the proton gradient in mitochondria? A) Pi-H+ symporter B) ATP synthase C) pyruvate translocase D) All of the answers are correct. E) None of the answers is correct.
D
Which of the following is an uncoupler for oxidative phosphorylation? A. Rotenone B. Cabon Monoxide C. Cyanide D. Dinitrophenol E. Oligomycin
D
Which of the following statements are true about oxidative phosphorylation? A. Electron transport provides energy to pump protons into the intermembrane space. B. An electrochemical gradient is formed across the inner mitochondrial membrane. C. Potassium and sodium ions form an ionic gradient across the inner mitochondrialmembrane. D. A and B E. A, B, and C
D
Which protein is NOT portion encoded in human mitochondrial DNA? A) Complex I (NADH dehydrogenase) B) Complex II (succinate dehydrogenase) C) Complex III (ubiquinone:cytochrome c oxidoreductase) D) cytochrome c E) Complex IV (cytochrome oxidase)
D
Which statement about energy conservation in the mitochondrion is FALSE? A) Drugs that inhibits the ATP synthase will also inhibit the flow of electrons down the chain of carriers. B) For oxidative phosphorylation to occur, it is essential to have a closed membranous structure with an inside and an outside. C) The yield of ATP per mole of oxidizable substrate depends on the substrate. D) Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitors such as cyanide; both block further electron transfer to oxygen. E) Uncouplers ìshort circuitî the proton gradient, thereby dissipating the proton motive force as heat.
D
Which statement is FALSE regarding 2,4-dinitrophenol? A) It is a proton carrier ionophore. B) It may be either neutral or negatively charged. C) It is soluble in the lipid core of membranes. D) It requires a specific transporter to enter mitochondria. E) It decreases ATP synthesis will increasing oxygen consumption.
D
Which statement is FALSE regarding flavoproteins? A) They may contain either FMN or FAD. B) The reduction potential of the flavin will depend on the amino acids in the polypeptide chain. C) They will need at least two substrates in order to function as enzymes. D) They are always integral membrane proteins. E) Most flavoproteins in electron transport have a lower reduction potential than coenzyme Q.
D
Which step is NOT part of the proton-translocation process in ATP synthase? A) A negatively charged amino acid in each c subunit becomes neutral upon proton binding. B) A positively charged amino acid in the a subunit forms an ion pair with a charged amino acid in a c subunit. C) Deprotonated c subunits are able to interact only with the a subunit. D) An arginine in the a subunit is reversibly protonated and deprotonated in each proton binding event. E) Proton direction is determined by the relative concentrations of protons on either side of the membrane.
D
A new compound isolated from mitochondria is claimed to represent a previously unrecognized carrier in the electron transfer chain. It is given the name coenzyme Z. Which line of evidence do you feel is the LEAST conclusive in assigning this compound a position in the electron transfer chain? A) Alternate oxidation and reduction of the mitochondrion-bound coenzyme Z can be readily demonstrated. B) Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen consumption. C) The rate of oxidation and reduction of mitochondrion-bound coenzyme is of the same order of magnitude as the overall rate of electron transfer in mitochondria as measured by oxygen consumption. D) The reduction potential of Z is between that of two compounds known to participate in the electron transport chain E) When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and specifically by the mitochondria.
E
Coenzyme Q is a prosthetic group for which of the following complexes in the electron transport chain? A) Complex I B) Complex II C) Complex III D) All of the answers are correct. E) None of the answers is correct
E
In normal mitochondria, the rate of NADH consumption (oxidation) will: A) be increased in active muscle, decreased in inactive muscle. B) be very low if the ATP synthase is inhibited, but increase when an uncoupler is added. C) decrease if mitochondrial ADP is depleted. D) decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex. E) All of the answers are correct.
E
In the final stage of the oxidation of food molecules, a gradient of protons is formed across theinner mitochondrial membrane, which is normally impermeable to protons. If cells areexposed to an agent that causes the membrane to become freely permeable to protons, whichof the following effects would you expect to observe? A. Cells would be completely unable to synthesize ATP. B. NADH would build up. C. Carbon dioxide production would cease. D. Consumption of oxygen would fall. E. The ratio of ATP to ADP in the cytoplasm would fall.
E
Oligomycin inhibits oxidative phosphorylation at A. Complex I B. Complex II C. Complex III D. Complex IV E. Complex V
E
The relative concentrations of ATP and ADP control the cellular rates of: A. glycolysis. B. oxidative phosphorylation. C. pyruvate oxidation. D. the citric acid cycle. E. all of the above.
E
The relative concentrations of ATP and ADP control the cellular rates of: A) glycolysis. B) oxidative phosphorylation. C) pyruvate oxidation. D) the citric acid cycle. E) All of the answers are correct.
E
Which of the following is correct concerning the mitochondrial ATP synthase? A) It can synthesize ATP after it is extracted from broken mitochondria. B) It catalyzes the formation of ATP even though the reaction has a large positive ΔG'°. C) It consists of F0 and F1 subunits, which are transmembrane (integral) polypeptides. D) It is actually an ATPase and only catalyzes the hydrolysis of ATP. E) When it catalyzes the ATP synthesis reaction, the ΔG'° is actually close to zero.
E
Which of the following statements about the chemiosmotic theory is false? A. Electron transfer in mitochondria is accompanied by an asymmetric release of protons on oneside of the inner mitochondrial membrane. B. Energy is conserved as a transmembrane pH gradient. C. Oxidative phosphorylation cannot occur in membrane-free preparations. D. The effect of uncoupling reagents is a consequence of their ability to carry protons throughmembranes. E. The membrane ATPase, which plays an important role in other hypotheses for energy coupling,has no significant role in the chemiosmotic theory.
E
Which of the following statements regarding electron transport are true? A. Only high-energy electrons from NADH can be used to drive the electron transport chain. B. The proteins involved in electron transport couple oxidation to phosphorylation in much the same way that glyceraldehyde 3-phosphate dehydrogenasecouples oxidation and phosphorylation in glycolysis. C. Electron transport occurs only in eukaryotes. D. Molecular oxygen is required in order to donate electrons to the electron transportchain. E. Electrons passing along the electron transport chain move to successivelylower energy states.
E
Which one of the following best describes the role of mitochondria in apoptosis? A) Escape of cytochrome c into the cytoplasm. B) Increased rate of fatty acid β-oxidation. C) Increase in permeability of outer membrane. D) Uncoupling of oxidative phosphorylation. E) Both A and C are correct.
E
Which phrase BEST describes the role of mitochondria in apoptosis? A) escape of cytochrome c into the cytoplasm B) increased rate of fatty acid β oxidation C) an increase in permeability of outer membrane D) uncoupling of oxidative phosphorylation E) both escape of cytochrome c into the cytoplasm and an increase in permeability of outer membrane
E
Which statement about the chemiosmotic theory is FALSE? A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. B) Energy is conserved as a transmembrane pH gradient. C) Oxidative phosphorylation cannot occur in membrane-free preparations. D) The effect of uncoupling reagents is a consequence of their ability to carry protons through membranes. E) The membrane ATPase, which plays an important role in other hypotheses for energy coupling, has no significant role in the chemiosmotic theory.
E
Which statement is CORRECT concerning the mitochondrial ATP synthase? A) It can synthesize ATP after it is extracted from broken mitochondria. B) It catalyzes the formation of ATP even though the reaction has a large positive ΔG'∞. C) It consists of Fo and F1 subunits, which are transmembrane (integral) polypeptides. D) It is actually an ATPase and only catalyzes the hydrolysis of ATP. E) When it catalyzes the ATP synthesis reaction, the ΔG'∞ is actually close to zero.
E
Which statement is FALSE concerning Complex III and the Q cycle? A) Both Q and QH2 are substrates for Complex III. B) Four protons are released on the P side of the membrane for every two electrons transferred to cytochrome c. C) This protein contains both iron-sulfur clusters and heme as prosthetic groups. D) Two protons from the matrix side are used to generate QH2 from the semiquinone radical. E) Overall, in each cycle one cytochrome c is reduced for every QH2 oxidized (net).
E
Which statement is FALSE regarding ATP synthase? A) The active site contains multiple positive charges that interact with the substrates. B) The energy difference between bound substrate and bound product is close to zero. C) As an enzyme, ATP synthase is classified as a hydrolase. D) ATP synthase can be classified as a primary active transporter. E) ADP binds more tightly to the active site than ATP.
E
Which statement is NOT a feature of Complex IV? A) Cytochrome c is a one-electron donor. B) Oxygen is a substrate. C) Copper is an essential metal for the reaction. D) For every electron passed to Complex IV, two protons are consumed from the matrix (N) side. E) In order to generate two water molecules, Complex IV must go through the catalytic cycle two times.
E
Which of the following statements best describes why electrons from FADH2 moving through the electron transport chain contribute less to the proton gradient than electrons from NADH?
FADH2 has a higher reduction potential than NADH and therefore its electrons must enter the electron transport chain downstream of NADH.
The cytochromes undergo which of the following oxidation reactions?
Fe2+ --> Fe3+
Cytochrome C carries electrons from complex _______ to complex _______. E. I; II F. II; III G. I; III H. III; IV
H
For eukaryotes, where are the Complexes of electron transport located?
Inner mitochondrial membrane
What is the path of electrons from NADH through the electron transport chain?
NADH, Complex I, Q, Complex III, CytC, Complex IV, O2
What is the correct order for the following substances in terms of reduction potential, greatest to least?
O2 > CoQ >FAD > NAD+
Cyanide blocks electron transport through complex IV. Which of the following will occur if cyanide is added to cells?
O2 consumption will decrease
Oligomycin is a substance that prevents the ATP synthesis reaction in oxidative phosphorylation, and 2,4-dinitrophenol is an uncoupling agent. In the presence of oligomycin, what would be the effect of adding 2,4-dinitrophenol?
O2 consumption will increase.
Which of the following statements regarding oxidative phosphorylation is TRUE?
Proton transfer through the Fo subunit of ATP synthase is required in order for ATP synthesis to occur.
The electron transport chain and the ATP synthase are effectively coupled. Which of the following statements best describes how this occurs?
The electron transport chain generates an electrochemical gradient that drives the production of ATP.
Which one of the following is NOT associated with electron transport?
coenzyme A
In the malate aspartate shuttle, _____ is transferred into the mitochondria while _____ is transferred to the cytosol.
malate; aspartate
What free radical is thought to be commonly produced by the electron transport chain?
superoxide
