Deck 14: Electron Transport and Atp Synthesis

Question 1

The enzyme complexes associated with oxidative phosphorylation and the electron transport chain can be classified as ________ proteins.

A)integral membrane
B)peripheral membrane
C)lipid-anchored membrane
D)water-soluble
E)Both A and C

Answer 1

integral membrane

Question 2

Which statement is true about two reactions that are coupled?

A)One reaction will normally not occur without the other.
B)One is always exergonic and the other is always endergonic.
C)Only oxidation-reduction reactions can be coupled.
D)Coupled reactions are always driven by the ATP to ADP conversion.

Answer 2

One reaction will normally not occur without the other.

Question 3

White muscle is exhausted faster than red muscle because white muscles

A)rely only on anaerobic glycolysis for energy.
B)have fewer mitochondria.
C)have no mitochondria.
D)cannot make ATP.

Answer 3

have fewer mitochondria.

Question 4

At one time the uncoupler 2,4-dinitrophenol was used as a weight reducing drug.Its side-effects,including death,resulted in its discontinued use.How could this drug cause weight loss?

A)The uncoupler allows the oxidation of fats from adipose tissue without the production of ATP.This allows the oxidation to proceed continuously and use up the fats.
B)The uncoupler causes ATP to be produced at a much higher rate than normal and this causes weight loss.
C)The uncoupler inhibits the transport of pyruvate into the matrix of the mitochondria.Fats are then degraded to glycerol and subsequently to pyruvate to provide the necessary energy,thereby depleting fat stores.
D)The uncoupler is an allosteric activator of ATP synthase.This increases the rate of translocation of H+ and the oxidation of fuels,including fats.

Question 5

In the presence of oxygen and in the absence of ADP,what occurs if the uncoupler 2,4-dinitrophenol is added to a suspension of normal mitochondria five minutes after an oxidizable substrate has been added?

A)The substrate will be oxidized until the addition of the 2,4-dinitrophenol,which blocks further oxidation.
B)There is no effect;oxidation of the substrate continues at the same rate before and after the addition of 2,4-dinitrophenol.
C)The substrate cannot be oxidized either with or without 2,4-dinitrophenol unless ADP is also present.
D)Oxidation of the substrate does not occur until the 2,4-dinitrophenol is added.Afterward,oxidation proceeds rapidly until all of the substrate is consumed.

Question 6

The chemiosmotic theory is a concept that ________.

A)the transport of Na+ and K+ across cell membranes is by active transport
B)explains how transport by facilitated diffusion reaches a saturation limit
C)explains the blood-brain barrier
D)a proton gradient drives the formation of ATP

Question 7

In prokaryotes what is the cellular location of the electron transport chain and ATP synthase complexes?

A)Plasma membrane.
B)Cytosol.
C)Inner mitochondrial membrane.
D)Endoplasmic reticulum.
E)Ribosome.

Question 8

The inner mitochondrial membrane contributes to the formation of a proton gradient mainly because it

A)contains ATP synthase complex.
B)is the location of specific transporter proteins.
C)is a barrier to protons.
D)is not rich in proteins.
E)is rich in proteins.

Question 9

The ________ is between the inner and outer membranes of the mitochondria.

A)matrix
B)intermembrane space
C)intracellular fluid
D)ATP synthase complex

Question 10

ATP synthase is located in the ________ of the mitochondrion.

A)outer membrane
B)inner membrane
C)matrix
D)intermembrane space

Question 11

The inner membrane of mitochondria is permeable to ________,but not to ________.

A)protons;water
B)cations;anions
C)charged molecules;uncharged molecules
D)uncharged molecules;charged molecules

Question 12

In eukaryotes what is the cellular location of the electron transport chain and ATP synthase complexes?

A)Plasma membrane.
B)Cytosol.
C)Inner mitochondrial membrane.
D)Endoplasmic reticulum.
E)Ribosome.

Question 13

In the mitochondria NADH and QH² are essentially oxidized by ________ since it is the terminal electron acceptor.

A)carbon dioxide
B)hydrogen peroxide
C)ozone
D)oxygen

Question 14

What is the pH difference (△pH)across a membrane at 310 K if the membrane potential is -0.15 V and the overall Gibb's free energy change across the membrane is -19 .0 kJ mol-1? (R = 8.315 J K-1 mol-1;F = 96,485 J V-1 mol-1)

A)5.44
B)2.3
C)0.74
D)1.4

Question 15

Which of the following is mismatched?

A)Outer mitochondrial membrane - permeable to ions and water.
B)Inner mitochondrial membrane - permeable to O₂ and CO₂.
C)Outer mitochondrial membrane - folded into cristae.
D)Inner mitochondrial membrane - location of ATP synthase.
E)Matrix - some ATP synthase subunits extend here.

Question 16

Oxidative phosphorylation requires all of the items listed below except

A)ATP synthase in the correct position in the membrane.
B)enzyme complexes embedded in a membrane.
C)the flow of electrons from NADH and QH₂ in the membrane.
D)a matrix more positively charged than the intermembrane space.
E)a terminal electron acceptor which is O₂ in mitochondria.

Question 17

What is the potential across a membrane if the overall Gibb's free energy change across the membrane is -19.3 kJ mol-1 and the pH difference across the membrane is 0.70 at 310K? (R = 8.315 J K-1 mol-1;F = 96,485 J V-1 mol-1)

A)-0.16 V
B)+.16 V
C)-0.24 V
D)+0.24 V

Question 18

Which of the following substances can freely pass through the inner mitochondrial membrane?

A)H⁺
B)Acetate
C)CO₂
D)ATP

Question 19

As electrons flow through complexes in the inner mitochondrial membrane,protons are moved from the matrix to the intermembrane space.This can make the pH

A)the same in the matrix and the inner membrane space.
B)lower in the matrix.
C)lower in both the matrix and the inner mitochondrial space.
D)lower in the inner membrane space.

Question 20

In the respiratory electron transport chain electrons are passed from ________.

A)NADH and QH₂ to O₂
B)O₂ to NAD+ and Q
C)O₂ to NADH
D)ATP to O₂

Question 21

Which is a component of complex I?

A)FAD
B)FMN
C)Q
D)TPP

Question 22

The chemiosmotic theory explains

A)the phosphorylation of ADP.
B)the electron transport chain.
C)the differences between inner and outer mitochondrial membranes.
D)the source of energy for formation of mitochondrial ATP.
E)aerobic respiration.

Question 23

Complex II in the electron transport chain supplies electrons as ________ to the rest of the chain (complexes III and IV).

A) FADH₂
B)Fe-S
C)succinate
D)QH₂

Question 24

The ultimate electron acceptor from complex II is ________.

A)Q
B)QH₂
C)cytochrome c
D)O₂
E)FMN

Question 25

The terminal electron acceptor for complex III of the electron transport chain is ________.

A)Q
B)Fe-S
C)FAD
D)cytochrome c

Question 26

What is the role of FMN in complex I?

A)Converts a two-electron transfer to a one-electron transfer.
B)Converts a one-electron transfer to a two-electron transfer.
C)Transports four H+ across the membrane.
D)None,there is no FMN in complex I.

Question 27

Which best describe the structure of complex II?

A)An L-shaped structure that spans the membrane and partially extends into the mitochondrial matrix.
B)A structure firmly anchored to the membrane by many α-helices that span the lipid-bilayer.
C)Three identical multisubunit enzymes that associate to form a mushroom-shaped structure.
D)Has a core structure of three conserved subunits,one of which forms a β-barrel on the exterior surface of the membrane.

Question 28

What is the Gibbs free energy change,△G,across a membrane with a pH difference of 0.50 and a membrane potential of -0.10 V at 310 K? (R = 8.315 J K-1 mol-1;F = 96,485 J V-1 mol-1)

A)-6.85 kJ mol-1
B)-12.6 kJ mol-1
C)38.6 kJ mol-1
D)57.9 kJ mol-1

Question 29

What feature of cytochromes makes them valuable in electron transport systems?

A)Aspartate residues in the active site.
B)The porphyrin ring.
C)The multiple α-helices.
D)The iron ion.

Question 30

To reduce one molecule of O₂,________ electron(s)must be passed through the electron transport chain and ________ molecule(s)of NADH is(are)oxidized.

A)4;2
B)2;1
C)1;1
D)1;2
E)4;4

Question 31

If the difference in pH across a membrane is 0.60 and the membrane potential is -0.10 V,about what percent of the Gibbs free energy change,△G,is from the pH difference at 37 oC? (R = 8.315 J K-1 mol-1;F = 96,485 J V-1 mol-1)

A)15%
B)27%
C)73%
D)85%

Question 32

During the Q-cycle ________ molecule(s)of QH² is(are)oxidized and ________ molecule(s)of Q is(are)produced.

A)1;1
B)1;2
C)2;1
D)2;2

Question 33

Which has the highest reduction potential?

A)NADH.
B)Complex I.
C)Complex II.
D)O².

Question 34

Which is not a component of complex II?

A)Fe-S clusters.
B)FAD.
C)Heme.
D)Cytochrome b.
E)All of the above are components of complex II.

Question 35

Iron sulfur clusters (Fs-S)that can accept or donate one electron are found in which complexes of the electron transport chain?

A)I
B)II and III
C)I,II and III
D)I,II,III and IV

Question 36

Energy from electron transport reactions is stored as a ________ gradient that is higher in the intermembrane space than in the mitochondrial matrix.

A)electron
B)ATP
C)proton
D)NADPH

Question 37

Which complex in the electron transport chain does not contribute to the proton gradient?

A)I
B)II
C)III
D)IV
E)V

Question 38

A lipid-soluble cofactor that can diffuse freely in the membrane of the electron transport chain and carry electrons across the membrane is ________.

A)ubiquinone (Q)
B)Fe-S
C)cytochrome c
D) FADH₂

Question 39

How many protons are translocated across the inner mitochondrial membrane by complex III for each pair of electrons passing through the electron transport chain?

A)0
B)1
C)2
D)4

Question 40

How many protons are translocated across the membrane by complex I for every pair of electrons that are passed from NADH to QH₂?

A)1
B)2
C)3
D)4
E)5

Question 41

The oxidizing agent in the enzyme superoxide dismutase is

A)superoxide anion (∙O₂-).
B)H₂O₂.
C)Copper.
D)O₂.
E)All of the above.

Question 42

Overall,the membrane-associated electron transport system pumps ________ protons across the membrane for every molecule of NADH that is oxidized.

A)2
B)5
C)6
D)10

Question 43

Which statement is not true about the transport of ATP across the inner mitochondrial membrane on its way to the cytosol?

A)It is accomplished by adenine nucleotide translocase.
B)The same enzyme that transports ATP also transport ADP in the opposite direction.
C)It is complexed with Mg₂+ to reduce the draw on the electrical part of the protonmotive force.
D)The transport causes the loss of a net charge of -1 in the matrix.

Question 44

Superoxide dismutase protects cells from damage caused by ________.

A)∙O²-
B)O₃²-
C)H₂O₂
D)H₃O+

Question 45

In mammals the enzyme complexes of oxidative phosphorylation are in the inner mitochondrial membrane.

Question 46

In the glycerol phosphate shuttle,reducing equivalents from NADH enter the electron transport system by reactions carrying electrons to ________.

A)complex III
B)complex IV
C)malate
D)complex I

Question 47

There are some eukaryotic species that do not have mitochondria.

Question 48

Rotation of the ________ subunit of ATP synthase causes conformational changes in the catalytic sites that produce ATP.

A)alpha
B)beta
C)gamma
D)F0

Question 49

Which complex in the electron transport chain carries electrons from cytochrome c to molecular oxygen,reducing it to water?

A)I
B)II
C)III
D)IV
E)V

Question 50

Electron transport chains occur only in the inner mitochondrial membrane of animal cells or the plasma membrane of bacteria.

Question 51

According to the binding change mechanism,the (alpha3 beta3 )oligomer of ATP synthase containing 3 catalytic sites can each have ________ different conformations.

A)2
B)3
C)6
D)9

Question 52

Heat can be generated in the brown adipose tissue of hibernating mammals due to ________.

A)increased ATP production by ATP synthase
B)uncoupling by thermogenin
C)a greater pH gradient across the inner mitochondrial membrane by complex IV
D)insufficient NADH production during the citric acid cycle due to less active pyruvate translocase.

Question 53

In bacteria,oxidative phosphorylation occurs in the mitochondrial membrane.

Question 54

How many protons are translocated across the inner mitochondrial membrane by complex IV for every pair of electrons passing through the electron transport chain?

A)0
B)1
C)2
D)3
E)4

Question 55

Which statement is false about complex IV?

A)A binuclear center that contains an iron ion and heme-a3 is the site of the reduction of molecular oxygen to water.
B)Bacterial and eukaryotic forms of complex IV have very similar structures and number of subunits per functional unit.
C)The core structure of the cytochrome c oxidase in complex IV has three conserved subunits.
D)Copper ions shift from a +2 oxidation state to a +1 oxidation state as electrons are passed through the complex.

Question 56

Which component of ATP synthase is the site of the proton channel?

A)F0.
B)F1.
C)F2.
D)B subunit.
E)G subunit.

Question 57

The P/O ratio for passing electrons through complexes I,III and IV is ________.

A)1
B)1.5
C)2
D)2.5
E)3

Question 58

Where is oxygen reduced with respect to Complex IV of the electron transport chain?

A)In the matrix itself,but close to a portion of Complex IV that extends into the matrix.
B)Near the inner membrane space side of the membrane on the surface of Complex IV.
C)Near the matrix side of the membrane on the surface of Complex IV.
D)At a site buried in the protein,but connected to the transport of electrons by a line of water molecules.
E)Freely in the hydrophobic portion of the lipid bilayer.

Question 59

The synthesis of one molecule of ATP from ADP requires ________ to be translocated across the inner mitochondrial membrane.

A)one proton
B)three protons
C)hundreds of protons
D)1 mole of protons

Question 60

The oxidation-reduction cofactor in the multisubunit enzyme fumarate reductase in E.coli which has the greatest reduction potential is

A)FAD.
B)iron clusters.
C)ubiquinone.
D)menaquinone.
E)NADH.

Question 61

Mitochondria are about the size of an E.coli cell.

Question 62

The number of mitochondria per cell is relatively constant among cell types and species.

Question 63

Most of the free energy needed to drive ATP formation in the mitochondria is the result of an electrical contribution from a charge gradient across the inner mitochondrial membrane.

Question 64

The enzyme complexes I-IV in the electron transport chain associate with each other by a combination of hydrophobic interactions,disulfide bridges and hydrogen bonding.

Question 65

Oxidative phosphorylation occurs in the mitochondrial membrane in eukaryotes and the plasma membrane in bacteria.

Question 66

Complex I contains a porin protein subunit that transports H+ across the inner mitochondrial membrane.

Question 67

If an inhibitor disrupts the flow of protons from the matrix into the intermembrane space of mitochondria,no ATP will be formed.

Question 68

In the presence of an uncoupler,more substrate can be oxidized.

Question 69

White muscle cells contain fewer mitochondria than red muscle cells,so they rely on anaerobic glycolysis for energy needs.

Question 70

The source of energy to produce ATP in mitochondria is a proton gradient formed across the outer mitochondrial membrane.

Question 71

The reactions in complex II release very little free energy and do not contribute directly to the proton concentration gradient.

Question 72

A muscle cell from an alligator jaw contains more mitochondria than a wing muscle of a migrating bird such as a goose.

Question 73

The chemiosmotic theory explains that the energy for driving ATP formation in mitochondria comes from a proton concentration gradient.

Question 74

Mitochondrial electron transport and ATP formation are interdependent.

Question 75

The protonmotive force is the free energy due to the proton gradient across the inner mitochondrial membrane.

Question 76

Membrane- associated electron transport complexes I and II are linked by ubiquinone (Q)while complexes II and IV are linked by cytochrome c.

Question 77

The inner mitochondrial membrane is permeable to water but the outer membrane is not.

Question 78

The reduction potential of Complex I is lower than that of Complex III.

Question 79

ATP directly provides the energy to transport protons across the inner membrane from the matrix to the intermembrane space of mitochondria.

Question 80

The numbers of mitochondria in cells is closely associated with cell function.