Deck 18: Oxidative Phosphorylation

Question 1

Which enzyme catalyzes the reduction of oxygen to water?

A) ATP synthase
B) cytochrome c oxidase
C) NADH-Q oxidoreductase
D) Q-cytochrome c oxidoreductase
E) succinate-Q reductase

Answer 1

B

Question 2

What term is used to describe an ATP-generating process in which an inorganic substance such as oxygen serves as the ultimate electron acceptor?

A) electron transport
B) respiration
C) fermentation
D) anaerobic phosphorylation
E) None of the answers is correct.

Answer 2

B

Question 3

What process allows cytoplasmic NADH to be reoxidized by O₂ using the electron-transport system?

A) glycerol 3-phosphate shuttle
B) cytochrome c shuttle
C) malate-aspartate shuttle
D) quinone shuttle
E) glycerol 3-phosphate shuttle and malate-aspartate shuttle

Answer 3

E

Question 4

Which enzyme transfers electrons from a membrane-soluble carrier to a water-soluble carrier in the electron-transport process?

A) ATP synthase
B) cytochrome c oxidase
C) NADH-Q oxidoreductase
D) Q-cytochrome c oxidoreductase
E) succinate-Q reductase

Question 5

What name is given to the hypothesis proposed by Peter Mitchell that explains how ATP synthesis is coupled to electron transport?

A) chemiosmotic hypothesis
B) oxidative phosphorylation hypothesis
C) electron transport hypothesis
D) proton-motive force hypothesis
E) None of the answers is correct.

Question 6

The unequal distribution of H⁺ across the inner mitochondrial membrane creates a ________________ force.

Question 7

In the initial step of Complex I, two high-potential electrons are transferred from NADH to the ___________ prosthetic group of this complex.

Question 8

What type of enzyme plays a key role in apoptosis?

A) cytochrome P450
B) electron-transport complexes
C) caspase
D) enzymes of the citric acid cycle
E) None of the answers is correct.

Question 9

_______________ is a molecular assembly in the inner mitochondrial membrane that carries out the synthesis of ATP.

Question 10

_________________ is a poison because it blocks the flow of electrons from cytochrome c to oxygen.

Question 11

Which of the citric acid cycle enzymes is also part of an electron-transport complex?

A) isocitrate dehydrogenase
B) $\alpha$ -ketoglutarate dehydrogenase
C) succinate dehydrogenase
D) malate dehydrogenase
E) None of the answers is correct.

Question 12

Cytochrome c oxidase contains two heme A groups and three ______________ ions.

Question 13

________________ carries electrons from Complex III to Complex IV.

Question 14

In the glycerol phosphate shuttle, cytoplasmic glycerol phosphate dehydrogenase uses cytoplasmic NADH to reduce _________________ to glycerol-3-phosphate.

Question 15

The transfer of a single electron to O₂ forms the reactive _______________ ion.

Question 16

Acceptor control of oxidative phosphorylation means that the rate of respiration depends upon the level of __________.

Question 17

Cytochrome ________ is the only water-soluble cytochrome of the electron-transport chain.

Question 18

What organelle is the site of oxidative phosphorylation in eukaryotes?

A) mitochondria
B) chloroplast
C) lysosome
D) endoplasmic reticulum
E) Golgi apparatus

Question 19

What prosthetic group is present in complexes I, II, and III of electron transport?

A) semiquinone
B) flavin mononucleotide
C) coenzyme Q
D) heme group
E) iron-sulfur cluster

Question 20

What type of protein makes the outer mitochondrial membrane relatively permeable?

A) proton pump
B) voltage gated transporter
C) ATP-powered pump
D) porin
E) None of the answers is correct.

Question 21

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 a-a₃ to oxygen is blocked.
C) Oligomycin blocks the proton transfer through F₀ of ATP synthase and therefore blocks the 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 lost as heat.

Question 22

Draw the structure of a mitochondrion and indicate the sites of oxidative phosphorylation and the citric acid cycle. Be sure to label your figure to clearly denote where these processes take place.

Question 23

The energy for ATP synthesis is generated by the movement of protons from the ______________ side of the inner mitochondrial membrane establishing a(an) _____________ gradient.

A) intermembrane; pH
B) intermembrane; electrical potential
C) matrix; sodium ion
D) matrix; pH
E) None of the answers is correct.

Question 24

What is a cytochrome?

A) a protein that transfers electrons and that also contains a heme prosthetic group
B) a chloroplast protein that transfers electrons and that also contains an iron sulfur prosthetic group
C) a protein that pumps ATP and that also contains iron
D) an enzyme that reduces oxygen to water
E) None of the answers is correct.

Question 25

In the Rieske center, the iron-sulfur center is coordinated to the amino acid(s) _______.

A) His
B) Cys
C) His and Cys
D) Cys and Met
E) None of the answers is correct.

Question 26

Which of the following does not pump protons?

A) Complex I
B) Complex II
C) Complex III
D) Complex IV
E) All of the answers are correct.

Question 27

What is the net ATP obtained from one cytoplasmic NADH when it is reoxidized by the electron-transport chain using the glycerol 3-phosphate shuttle?

A) 2.5
B) 1.5
C) 2.0
D) 1.0
E) None of the answers is correct.

Question 28

In prokaryotes the site of ATP-synthesizing machinery is

A) the mitochondrial matrix.
B) the outer cell wall.
C) the cytoplasmic membrane.
D) the nucleolus.
E) None of the answers is correct.

Question 29

Explain why less ATP is made from the reoxidation of FADH₂ as compared to NADH.

Question 30

Electron flow down the electron-transport chain leads to the

A) transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space.
B) transport of protons across the inner mitochondrial membrane from the intermembrane space into the matrix.
C) coupled synthesis of GTP.
D) a dangerous imbalance of K⁺ ions across the mitochondrial membrane.
E) None of the answers is correct.

Question 31

Which electron carrier has an isoprenoid tail?

A) NADH
B) cytochrome c
C) coenzyme Q
D) FADH^?₂
E) None of the answers is correct.

Question 32

What is the driving force for electron transport through the electron-transport chain?

Question 33

Choose the correct path taken by a pair of electrons as it travels down the electron-transport chain.

A) NADH $\rightarrow$ Complex I $\rightarrow$ CoQ $\rightarrow$ Complex III $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O₂
B) FADH₂ $\rightarrow$ Complex I $\rightarrow$ CoQ $\rightarrow$ Complex III $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O₂
C) NADH $\rightarrow$ Complex I $\rightarrow$ Complex II $\rightarrow$ Complex III $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O₂
D) FADH₂ $\rightarrow$ Complex III $\rightarrow$ CoQ $\rightarrow$ Complex II $\rightarrow$ Cyt c $\rightarrow$ Complex IV $\rightarrow$ O₂
E) None of the answers is correct.

Question 34

What is the currently accepted model which explains the presence of mitochondria in eukaryotic cells? What is the best evidence which supports this model?

Question 35

When glucose is totally oxidized to CO₂ and H₂O and the glycerol 3-phosphate shuttle is used, how many ATP molecules are made by oxidative phosphorylation (nonsubstrate-level phosphorylation) relative to the maximum yield?

A) 12 out of 30
B) 26 out of 30
C) 26 out of 32
D) 12 out of 32
E) None of the answers is correct.

Question 36

In the malate-aspartate shuttle, electrons from NADH are transferred to ________, forming malate.

A) oxaloacetate
B) aspartate
C) acetate
D) glutamate
E) None of the answers is correct.

Question 37

What type of gradient is critical to ATP formation by oxidative phosphorylation?

A) sodium ion
B) chloride ion
C) proton
D) potassium ion
E) None of the answers is correct.

Question 38

Provide a brief description of oxidative phosphorylation.

Question 39

Which of the following does NOT participate in, nor is a component of, the electron-transport chain?

A) lipoic acid
B) nonheme, iron-sulfur proteins
C) FADH₂
D) cytochrome c₁
E) NADH

Question 40

What is the reaction of ATP synthase?

A) AMP^3- + 2 HPO₄^2- + H⁺ $\iff$ ATP^4- + H₂O
B) ADP^3- + HPO₄^2-+ H⁺ $\iff$ ATP^4-+ H₂O
C) ADP^3- + HPO₄^2- + 2 H⁺ $\iff$ ATP^4- + H₂O
D) AMP^3- + 2 HPO₄^2- + 2 H⁺ $\iff$ ATP^4- + H₂O
E) None of the answers is correct.

Question 41

Discuss the evolution of the cytochrome c protein.

Question 42

Give the balanced equation for the net reaction catalyzed by Q-cytochrome c oxido-reducatase.

Question 43

Explain why carbon monoxide is toxic.

Question 44

How is oxidative phosphorylation regulated?

Question 45

Describe the major defensive strategy that cells employ to prevent the harmful effects of the reactive oxygen species (ROS) that are inevitably produced during respiration.

Question 46

Describe the function of protons in the mechanism of ATP synthesis by the F₁ subunit of ATP synthase.

Question 47

What are uncoupling agents? Provide an example of when these might be useful.

Question 48

How does the glycerol 3-phosphate shuttle function?

Question 49

What evidence demonstrated the ATP synthase has components that can actually rotate?

Question 50

In the malate-aspartate shuttle, how is oxaloacetate regenerated since there is no transporter for oxaloacetate across the inner membrane?