Biochem

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1

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

  1. A) carbon dioxide
  2. B) hydrogen peroxide
  3. C) ozone
  4. D) oxygen
  1. D) oxygen
2

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.

D) lower in the inner membrane space.

3

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.

A) Plasma membrane.

4

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

  1. A) Plasma membrane.
  2. B) Cytosol.
  3. C) Inner mitochondrial membrane.
  4. D) Endoplasmic reticulum.
  5. E) Ribosome.

C) Inner mitochondrial membrane.

5

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

A) integral membrane

6

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

  1. A) H+
  2. B) Acetate
  3. C) CO2
  4. D) ATP

C) CO2

7

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

  1. A) NADH and QH2to O2
  2. B) O2to NAD+and Q
  3. C) O2to NADH
  4. D) ATP to O2
  1. A) NADH and QH2to O2
8

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.

B) have fewer mitochondria.

9

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

A) matrix

B) intermembrane space

C) intracellular fluid

D) ATP synthase complex

B) intermembrane space

10

Oxidative phosphorylation requires all of the items listed below except

  1. A) ATP synthase in the correct position in the membrane.
  2. B) enzyme complexes embedded in a membrane.
  3. C) the flow of electrons from NADH and QH2in the membrane.
  4. D) a matrix more positively charged than the intermembrane space.
  5. E) a terminal electron acceptor which is O2in mitochondria.

D) a matrix more positively charged than the intermembrane space.

11

ATP synthase is located in the ________ of the mitochondrion.

A) outer membrane

B) inner membrane

C) matrix

D) intermembrane space

B) inner membrane

12

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

D) uncharged molecules; charged molecules

13

Which of the following is mismatched?

  1. A) Outer mitochondrial membrane - permeable to ions and water.
  2. B) Inner mitochondrial membrane - permeable to O2and CO2.
  3. C) Outer mitochondrial membrane - folded into cristae.
  4. D) Inner mitochondrial membrane - location of ATP synthase.
  5. E) Matrix - some ATP synthase subunits extend here.

C) Outer mitochondrial membrane - folded into cristae.

14

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

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

C) is a barrier to protons.

15

The chemiosmotic theory is a concept that ________.

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

D) a proton gradient drives the formation of ATP

16

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.

A) One reaction will normally not occur without the other.

17

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.

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

18

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.

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.

19

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)

  1. A) 5.44
  2. B) 2.3
  3. C) 0.74
  4. D) 1.4

C) 0.74

20

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)

  1. A) -0.16 V
  2. B) +.16 V
  3. C) -0.24 V
  4. D) +0.24 V

A) -0.16 V

21

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)

  1. A) 15%
  2. B) 27%
  3. C) 73%
  4. D) 85%

B) 27%

22

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)

  1. A) -6.85 kJ mol-1
  2. B) -12.6 kJ mol-1
  3. C) 38.6 kJ mol-1
  4. D) 57.9 kJ mol-1
  1. B) -12.6 kJ mol-1
23

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

  1. A) electron
  2. B) ATP
  3. C) proton
  4. D) NADPH

C) proton

24

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.

D) the source of energy for formation of mitochondrial ATP.

25

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

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

D) The iron ion.

26

Which has the highest reduction potential?

  1. A) NADH.
  2. B) Complex I.
  3. C) Complex II.
  4. D) O2.
  1. D) O2.
27

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

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

A) 4; 2

28

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

  1. A) ubiquinone (Q)
  2. B) Fe-S
  3. C) cytochrome c
  4. D) FADH2

A) ubiquinone (Q)

29

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

  1. A) I
  2. B) II and III
  3. C) I, II and III
  4. D) I, II, III and IV

C) I, II and III

30

Which is a component of complex I?

A) FAD

B) FMN

C) Q

D) TPP

B) FMN

31

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.

A) Converts a two-electron transfer to a one-electron transfer.

32

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

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

D) 4

33

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

  1. A) I
  2. B) II
  3. C) III
  4. D) IV
  5. E) V

B) II

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.

D) Cytochrome b.

35

The ultimate electron acceptor from complex II is ________.

  1. A) Q
  2. B) QH2
  3. C) cytochrome c
  4. D) O2
  5. E) FMN

A) Q

36

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.

C) Three identical multisubunit enzymes that associate to form a mushroom-shaped structure.

37

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

  1. A) FADH2
  2. B) Fe-S
  3. C) succinate
  4. D) QH2
  1. D) QH2
38

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

A) Q

B) Fe-S

C) FAD

D) cytochrome c

D) cytochrome c

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

D) 4

40

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

  1. A) 1; 1
  2. B) 1; 2
  3. C) 2; 1
  4. D) 2; 2

C) 2; 1

41

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

D) IV

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

D) 10

43

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.

B) Bacterial and eukaryotic forms of complex IV have very similar structures and number of subunits per functional unit.

44

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

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

Answer

C) 2

45

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.

D) At a site buried in the protein, but connected to the transport of electrons by a line of water molecules.

46

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

B) three protons

47

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

C) gamma

48

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

B) 3

49

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.

B) uncoupling by thermogenin

50

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

A) F0.

B) F1.

C) F2.

D) B subunit.

E) G subunit.

A) F0.

51

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

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

C) It is complexed with Mg2+ to reduce the draw on the electrical part of the protonmotive force.

52

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

D) 2.5

53

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

A) complex III

54

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.

D) menaquinone.

55

The oxidizing agent in the enzyme superoxide dismutase is

  1. A) superoxide anion (∙O2-).
  2. B) H2O2.
  3. C) Copper.
  4. D) O2.
  5. E) All of the above.

C) Copper.

56

Superoxide dismutase protects cells from damage caused by ________.

  1. A) ∙O2-
  2. B) O32-
  3. C) H2O2
  4. D) H3O+

A) ∙O2-