Biochem B: Chapter 14

Calculate ΔG for ATP hydrolysis at 37 ∘C under these conditions. The energy charge is the concentration of ATP plus half the concentration of ADP divided by the total adenine nucleotide concentration: [ATP]+1/2[ADP]/[ATP]+[ADP]+[AMP]

ΔG=-47.3 kJ/mol

Calculate the net standard free energy change (ΔG∘′) in this system, using E′0 values from Table 14.1 in the textbook and a ΔG∘′ value for ATP hydrolysis of -32.2 kJ/mol.

ΔG∘′ = -51.4 kJ/mol

Calculate the standard free energy change as a pair of electrons is transferred from succinate to molecular oxygen in the mitochondrial respiratory chain.

-152 kJ/mol

Identify the complexes and mobile electron carriers that remain reduced and oxidized due to the following blocker/inhibitors. You can use the electron-transport chain labeled in part A to help answer this question. 1. Amytal is a painkiller that blocks the flow of electrons to coenzyme Q. 2. Cyanide is a poison that blocks the flow of electrons to oxygen/Complex IV. 3. Antimycin is an antibiotic that blocks the flow of electrons to Cytochrome c. 4. Rotenone is an insecticide that blocks the flow of electrons to Coenzyme Q. For each of these Last component that can be reduced due to inhibitor/blocker... Last component that remains oxidized due to inhibitor/blocker... Options: Complex I Complex III Coenzyme Q Complex IV Cytochrome c

1. Complex 1 & Coenzyme Q 2. Cytochrome c & Complex IV 3. Complex III & Cytochrome c 4. Complex I & Coenzyme Q

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.

2

Based on your answer in part A, calculate the maximum number of protons that could be pumped out of the matrix into the intermembrane space as these electrons are passed to oxygen. Assume 25 ∘C, ΔpH=1.4; Δψ= 0.175 V (matrix negative).

6 protons

What would ΔG∘′ be for an enzyme that oxidizes succinate with NAD+ instead of FAD?

67.5 kJ/mol

During electron transport, energy from _____ is used to pump hydrogen ions into the _____. acetyl CoA...intermembrane space NADH...intermembrane spae NADH and FADH2...intermembrane space NADH...mitochondrial matrix NADH and FADH2...mitochondrial matrix

NADH and FADH2...intermembrane space

Under these conditions, what P/O ratio would you expect to observe?

P/O ratio = 3.5

Label the steps of electron transport leading to oxidative phosphorylation where ATP is synthesized from ADP using the energy stored by the electron-transport chain.

See picture

In animal cells the mitochondrial electron transport chain is responsible for reoxidizing most of the NADH produced by oxidative pathways regardless of the cellular compartment in which it was produced. True or false?

True

Part complete CoQ carries electrons from NADH-Coenzyme Q reductase and succinate dehydrogenase as well as other flavoproteins to CoQ:Cytochrome c oxidoreductase. True or false?

True

Arrange the sequence of events that occur in complex I in their proper order. 1) Fe+2 is oxidized to Fe+3. 2) FMN is reduced to FMNH2. 3) NADH is oxidized to NAD+. 4) CoQ is reduced to CoQH2. a. 3, 2, 1, 4 b. 3, 2, 4, 1 c. 3, 4, 2, 1 d. 3, 1, 2, 4

a. 3, 2, 1, 4

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation

The final electron acceptor of cellular respiration is _____.

oxygen

At which site(s) are these protons pumped?

pumped to complexes III and IV

If the intramitochondrial concentration of succinate was 10-fold higher than that of fumarate, what minimum [NAD+]/[NADH] ratio in mitochondria would be needed to make this reaction exergonic at 37 ∘C?

2.5*10^10

Referring to Table 14.1 in the textbook for E′0 values, calculate ΔG∘′ for oxidation of malate by malate dehydrogenase.

29 kJ/mol

What is the total number of ATP molecules that can be produced from the complete oxidation of one glucose molecule?

32 or 36

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

6

Arrange the following steps or substances by where they appear in the process of glucose metabolism. options: the citric acid cycle, ATP synthase, glycolysis, electron transport chain Rank items from first to last.

Glycolysis -> Citric acid cycle -> electron transport chain -> ATP synthase

Match each compound with the complex it inhibits. 1) rotenone A) complex IV 2) CO B) complex III 3) antimycin C) complex I 4) cyanide 5) amytal a. 1:B; 2:C; 3:A; 4:A; 5:C b. 1:C; 2:A; 3:B; 4:A; 5:C c. 1:B; 2:A; 3:C; 4:C; 5:B d. 1:C; 2:B; 3:A; 4:A; 5:C

b. 1:C; 2:A; 3:B; 4:A; 5:C

What does this experiment tell you about the location of coupling sites for oxidative phosphorylation? a. Because ADP is consumed, with a P/O ratio of ~1.0, complex III must be a coupling site (i.e., a site of electron pumping). b. Because ATP is formed, with a P/O ratio of ~1.0, complex IV must be a coupling site (i.e., a site of proton pumping). c. Because ADP is formed, with a P/O ratio of ~1.0, complex IV must be a coupling site (i.e., a site of electron pumping). d. Because ATP is consumed, with a P/O ratio of ~1.0, complex III must be a coupling site (i.e., a site of proton pumping).

b. Because ATP is formed, with a P/O ratio of ~1.0, complex IV must be a coupling site (i.e., a site of proton pumping).

Part complete Why is β-hydroxybutyrate added rather than NADH? a. Because NADH cannot freely enter the vacuole. b. Because NADH cannot freely enter the mitochondrion. c. Because β-hydroxybutyrate cannot freely enter the mitochondrion. d. Because β-hydroxybutyrate cannot freely enter the vacuole.

b. Because NADH cannot freely enter the mitochondrion.

Briefly explain your answer. a. [NAD+]/[NADH] and [NADP+]/[NADPH] are equal. b. E∘′ for NAD+/NADH is the same as for NADP+/NADPH. c. The sum of E∘′ for NAD+/NADH and NADP+/NADPH is equal to zero. d. ΔG∘′ for this kind of processes do not depend on the specific compound and are always equal to each other.

b. E∘′ for NAD+/NADH is the same as for NADP+/NADPH.

Examine the molecular model of the partial structure of the yeast ATP synthase. Which part of the molecule spans the inner mitochondrial membrane? a. axle b. F0 rotor c. central stalk d. F1 catalytic complex

b. F0 rotor

Which statements about complex IV are true? 1) This complex catalyzes the reduction of oxygen to water. 2) Despite consuming protons, this complex pumps H+ across the membrane at a rate of 4 per molecule of O2 reduced. 3) The protons flow across a gradient to the inner membrane space. 4) Conformational changes as electrons flow through the complex alter the ability of some residues to bind protons. A. Statements 1, 2, and 4 are correct. B. Statements 1 and 4 are correct. C. Statements 1, 2, and 3 are correct. D. Statements 2, 3, and 4 are correct.

C. Statements 1, 2, and 3 are correct.

Suppose that a cell contained an isoform of glutathione reductase that used NADH instead of NADPH as the reductive coenzyme. Would you expect ΔG∘′ for this enzyme to be higher, lower, or the same as the corresponding value for the real glutathione reductase? a. ΔG∘′ would be higher. b. ΔG∘′ would be lower. c. ΔG∘′ would be the same.

c. ΔG∘′ would be the same.

Structure A is _____. an electron acceptor ATP synthase an electron donor sensory protein phospholipid

ATP synthase

Which state probably predominates in heart muscle most of the time? a. state 1 b. state 2 c. state 3 d. state 4 e. state 5

c. state 3 (rapid ATP production and turnover demand and continuous O2 uptake)

Which antibiotic, nigericin or valinomycin, do you predict to have the greatest effect on oxidative phosphorylation when administered to respiring mitochondria? Assume the antibiotics are added to a suspension of mitochondria in equimolar amounts. Briefly explain your reasoning. a. Because the pH gradient (ΔpH) makes a greater contribution to the electron motive force than the electrical component (Δψ), nigericin would be expected to be a more effective uncoupler than valinomycin. b. Because only the pH gradient (ΔpH) makes a contribution to the proton motive force, nigericin would be expected to be a more effective uncoupler than valinomycin. c. Because only the electrical component (Δψ) makes a contribution to the proton motive force, valinomycin would be expected to be a more effective uncoupler than nigericin. d. Because the electrical component (Δψ) makes a greater contribution to the proton motive force than the pH gradient (ΔpH), valinomycin would be expected to be a more effective uncoupler than nigericin. e. Because the pH gradient (ΔpH) makes a greater contribution to the electron motive force than the electrical component (Δψ), valinomycin would be expected to be a more effective uncoupler than nigericin. f. Because the electrical component (Δψ) makes a greater contribution to the proton motive force than the pH gradient (ΔpH), nigericin would be expected to be a more effective uncoupler than valinomycin.

d. Because the electrical component (Δψ) makes a greater contribution to the proton motive force than the pH gradient (ΔpH), valinomycin would be expected to be a more effective uncoupler than nigericin.

Examine the F1 complex of the ATP synthase from bovine heart mitochondria. What prevents this F1 complex from rotating with the F0 c-ring complex? a. Nothing prevents it. The F1 complex rotates with the F0 c-ring complex. b. It is bound within the inner mitochondrial membrane. c. It is bound to the central stalk. d. It is bound by the stator, which is connected to the stationary "a" subunit of F0.

d. It is bound by the stator, which is connected to the stationary "a" subunit of F0.

Coenzyme Q carries electrons between which stages of the electron-transport chain? Check all that apply. Complex III and complex IV Complex II and complex III Complex I and complex II Complex I and complex III

Complex II and complex III Complex I and complex III

As a representation of the respiratory chain, what is wrong with this picture? There are four deliberate errors. Check all that apply: NADH is oxidized by FMN, not FAD. NADH is oxidized by CoQ, not FAD. Cyt c1 accepts e− from cyt b, and is then oxidized by cyt c. O2 is reduced to H2O, not H2O2. O2 is oxidized to H2O, not H2O2. Cyt c1 accepts H+ from cyt b, and is then oxidized by cyt c. O2 is reduced to O2−2, not H2O2. Reduced flavin (FADH2 or FMNH2) is oxidized by CoQH, not CoQH2. NADH is oxidized by FADH2, not FAD. Reduced flavin (FADH2 or FMNH2) is oxidized by FAD, not CoQH2. Reduced flavin (FADH2 or FMNH2) is oxidized by CoQ, not CoQH2. Cyt c1 accepts e− from cyt a-a3, and is then oxidized by cyt b.

NADH is oxidized by FMN, not FAD. Cyt c1 accepts e− from cyt b, and is then oxidized by cyt c. O2 is reduced to H2O, not H2O2. Reduced flavin (FADH2 or FMNH2) is oxidized by CoQ, not CoQH2.

Which of the following is NOT true of respiratory control? a. Maintenance of respiratory control depends on the structural integrity of the mitochondrial inner membrane. b. The stimulation of respiration by addition of ADP is stoichiometric. c. The rate of respiration is controlled by the balance between the ΔG's for phosphorylation of ADP, electron transport and proton pumping. d. Oxidative phosphorylation is regulated by allosteric mechanisms. e. Oxidative phosphorylation is absolutely dependent on the continued flow of electrons from substrates to oxygen.

d. Oxidative phosphorylation is regulated by allosteric mechanisms.

What would the P/O ratio be if the same experiment were run with addition to the mitochondria of 2,4-dinitrophenol?

P/O ratio = 0

Referring to the following figure, predict the P/O ratio for oxidation of ascorbate by isolated mitochondria.

P/O ratio = 0.5

What does this mean? Identify and discuss an important implication of this conclusion. DNP acts catalytically in the sense that one DNP molecule can mediate the transport of __________ into the matrix: after __________ in the matrix (due to __________), DNP cycles back across the membrane to bind and bring another _________ into the matrix. One important implication is that DNP is _______________ in very small amounts. options: proton multiple electrons multiple hydroxide ions the lower pH toxic nontoxic deprotonating the higher pH multiple protons hydroxide ions

multiple protons; deprotonating; the higher pH; proton toxic

Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential.

positive

Four electron carriers, a, b, c, and d, whose reduced and oxidized forms can be distinguished spectrophotometrically, are required for respiration in a bacterial electron-transport system. In the presence of substrates and oxygen, three different inhibitors block respiration, yielding the patterns of oxidation states shown below. What is the order of the carriers in the chain from substrates to O2, and where do the three inhibitors act? a b c d substrates → ____ → _____ → _____ → _____ → oxygen

substrates → c → b → a → d → oxygen

If ADP is five times more abundant than AMP, calculate the molar concentrations of AMP at an energy charge of 0.85.

[AMP] = 2.9*10^-4 M

From E∘′ values in Table 14.1 in the textbook, calculate the equilibrium constant for the glutathione peroxidase reaction at 37 ∘C.

1.7*10^17

How many moles of ATP would you expect to be formed per mole of β-hydroxybutyrate oxidized in this system?

2 mol

All of the cytochromes in the mitochondrial respiratory chain contain the same heme moiety as found in hemoglobin. True or false?

False

The ATP yield from NADH transported across the mitochondrial inner membrane by the glycerol phosphate shuttle is the same as if the malate/aspartate shuttle were used. True or False?

False

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

False

Proton-driven rotation of the c-ring of the F0 unit of the F1F0 ATP synthase is required for complete passage of protons from the intermembrane space to the matrix. True or false?

True

Which of the following is NOT involved in the enzymatic inactivation of reactive oxygen species? a. Peroxiredoxin b. Peroxidase c. Superoxide dismutase d. Vitamin C e. Catalase

d. Vitamin C

Calculate the standard free energy change for the reaction FADH2 + 1/2O2 → FAD + H2O given that the standard reduction potential for the reduction of oxygen to water is +0.82 V and for the reduction of FAD to FADH2 is +0.03 V.

-152 kJ/mol

Calculate ΔG∘′ for the glutathione reductase reaction in the direction shown, using E∘′ values from Table 14.1 in the textbook.

-17.4 kJ/mol

Biochemists working with isolated mitochondria recognize five energy "states" of mitochondria, depending on the presence or absence of essential substrates for respiration−O2, ADP, oxidizable substrates, and so forth. The characteristics of each state are: state 1: mitochondria alone (in buffer containing Pi) state 2: mitochondria + substrate, but respiration low due to lack of ADP state 3: mitochondria + substrate + limited amount of ADP, allowing rapid respiration state 4: mitochondria + substrate, but all ADP converted to ATP, so respiration slows state 5: mitochondria + substrate + ADP, but all O2 used up (anoxia), so respiration stops On the graph, identify the state that might predominate in each stage of the trace indicated with a letter. A: B: C: D: E:

A: State 1 B: State 2 C: State 3 D: State 4 E: State 5

Thinking back to your lessons in metabolism, you know that metabolic pathways typically run in both directions. Some of these steps use the same enzyme for both directions. Other steps must use different enzymes and, therefore, serve as a key step for regulation to control flow either up or down the pathway. Which two of the above steps would you most expect to serve as key steps for kinetic control? Choose all that apply. Between C and D Between D and E Between B and C Between A and B

Between C and D Between B and C

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

False

The cell uses organelles to sequester reactions and concentrate reactants. Match each stage of cellular respiration with its location in the cell. Glycolysis Oxidative phosphorylation Citric acid cycle Locations: Cytosol Lysosome Mitochondrial matrix Inner mitochondrial matrix

Glycolysis takes place in the cytosol. Citric acid cycle takes place in the mitochondrial matrix. Oxidative phosphorylation takes place in the inner mitochondrial matrix.

Rank the following molecules by the number of ATP molecules they produce. Rank highest to lowest. Options: FADH2, GTP, NADH, acetyl CoA, pyruvate

Pyruvate > Acetyl CoA > NADH > FADH2 > GTP

When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (Assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.) Options: size of the proton gradient, rate of oxygen uptake, electron transport rate, rate of ATP synthesis, proton pumping Bins: remains the same, decreases (or goes to zero), increases

Remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake decreases or goes to zero: rate of ATP synthesis, size of protein gradient

In the diagram below, the red arrows show the flow of energy through the electron-transport chain. Follow the flow of electrons through the electron-transport chain, and label the components of the chain. options: complex I complex II cytochrome c ATP synthase complex IV coenzyme Q complex III

See picture Along the top: Coenzyme Q and Cytochrome c Along the bottom: complex I, complex II, complex III, complex IV, ATP synthase

The citric acid cycle can be broken into three stages. In the first stage, metabolic fuels (fats, amino acids, sugars) are converted into a common currency that is used by the second stage. The second stage is a substrate cycle in the mitochondrial matrix: the citric acid cycle proper. The third stage occurs in the inner mitochondrial membrane and is the principle source of cellular energy. Match the following features to the stage in which they can be found. Options: Conversion of pyruvate to acetyl-CoA Oxidation of NADH and FADH2 back to NAD+ and FAD Production of two molecules of CO2 Production of one molecule of CO2 Joining of acetyl-CoA to oxaloacetate Reduction of oxygen to water Primary source of ATP production Stage 1: Stage 2: Stage 3:

Stage 1: Conversion of pyruvate to acetyl-CoA and production of one molecule of CO2. Stage 2: Joining of acetyl-CoA to oxaloacetate and production of two molecules of CO2. Stage 3: Oxidation of NADH and FADH2 back to NAD+ and FAD, reduction of oxygen to water, and the primary source of ATP production.

In the early days of "mitochondriology", P/O ratios were determined from measurements of volume of O2 taken up by respiring mitochondria and chemical assays for disappearance of inorganic phosphate. Now, however, it is possible to measure P/O ratios simply with a recording oxygen electrode. How might this be done? a. Add ADP in limiting amount and measure O2 uptake. The ratio of μmol ADP consumed to μatom oxygen taken up is identical to the P/O ratio. b. Add ATP in limiting amount and measure O2 uptake. The ratio of μatom ATP consumed to μmol oxygen taken up is identical to the P/O ratio. c. Add ADP in excess amount and measure O2 uptake. The ratio of μmol ADP consumed to μmol oxygen taken up is identical to the P/O ratio. d. Add ATP in excess amount and measure O2 uptake. The ratio of μatom ATP consumed to μmol oxygen taken up is identical to the P/O ratio.

a. Add ADP in limiting amount and measure O2 uptake. The ratio of μmol ADP consumed to μatom oxygen taken up is identical to the P/O ratio.

How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.) a. Both electron transport and ATP synthesis would stop. b. Electron transport would stop but ATP synthesis would be unaffected. c. Electron transport would be unaffected but ATP synthesis would stop. d. Neither electron transport nor ATP synthesis would be affected.

a. Both electron transport and ATP synthesis would stop.

Under anaerobic conditions (a lack of oxygen), glycolysis continues in most cells despite the fact that oxidative phosphorylation stops, and its production of NAD+ (which is needed as an input to glycolysis) also stops. The diagram illustrates the process of fermentation, which is used by many cells in the absence of oxygen. In fermentation, the NADH produced by glycolysis is used to reduce the pyruvate produced by glycolysis to either lactate or ethanol. Fermentation results in a net production of 2 ATP per glucose molecule. During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell's demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions. a. Glucose utilization would increase a lot. b. Glucose utilization would increase a little. c. Glucose utilization would remain the same. d. Glucose utilization would decrease a little. e. Glucose utilization would decrease a lot.

a. Glucose utilization would increase a lot.

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops. a. In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration. b. Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made. c. Oxygen is an input to acetyl CoA formation. d. ATP is needed to convert pyruvate to acetyl CoA. Without oxygen, no ATP can be made in oxidative phosphorylation.

a. In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration.

Which statement about uncouplers is NOT true? a. They allow ATP synthesis with no electron transport. b. They allow electron transport without ATP synthesis. c. Their mechanism of action is basically to transport protons back into the matrix, preventing the required buildup of charge on the other side. d. 2,4-DNP is an example of an uncoupler.

a. They allow ATP synthesis with no electron transport.

If you were to determine the P/O ratio for oxidation of α-ketoglutarate, you would probably include some malonate in your reaction system. Why? a. To block succinate dehydrogenase and measure phosphorylation resulting only from the α-ketoglutarate dehydrogenase reaction. b. To catalyze cytochrome c and measure phosphorylation resulting only from the α-ketoglutarate hydrogenase reaction. c. To block cytochrome c and measure dephosphorylation resulting only from the α-ketoglutarate hydrogenase reaction. d. To catalyze succinate dehydrogenase and measure dephosphorylation resulting only from the α-ketoglutarate dehydrogenase reaction.

a. To block succinate dehydrogenase and measure phosphorylation resulting only from the α-ketoglutarate dehydrogenase reaction.

The proximate (immediate) source of energy for oxidative phosphorylation is _____. a. kinetic energy that is released as hydrogen ions diffuse down their concentration gradient. b. NADH and FADH2 c. ATP synthase d. substrate-level phosphorylation e. ATP

a. kinetic energy that is released as hydrogen ions diffuse down their concentration gradient.

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis? a. proton gradient b. electrons c. osmotic gradient d. temperature gradient

a. proton gradient

Which of the following particles can pass through the ATP synthase channel? a. protons b. inorganic phosphate c. ADP d. ATP

a. protons

What is the source of energy that directly drives ATP synthase in its production of ATP? a. protons diffusing through the F0 section of ATP synthase b. the hydrolysis of ATP c. the oxidation of NADH d. the oxidation of FADH2 e. the oxidation of glucose

a. protons diffusing through the F0 section of ATP synthase

The four stages of cellular respiration do not function independently. Instead, they are coupled together because one or more outputs from one stage functions as an input to another stage. The coupling works in both directions, as indicated by the arrows in the diagram below. In this activity, you will identify the compounds that couple the stages of cellular respiration.

a. pyruvate b. NADH c. NAD+ d. NADH e. NAD+

Given what you know about the metabolic roles and/or intracellular concentration ratios of NAD+/NADH and NADP+/NADPH, would you expect ΔG (not ΔG∘′) for this enzyme to be higher, lower, or the same as ΔG for the real enzyme under intracellular conditions? a. ΔG would be higher. b. ΔG would be lower. c. ΔG would be the same.

a. ΔG would be higher.

NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. a. There is more NADH than FADH2 made for every glucose that enters cellular respiration. b. Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor. c. It takes more energy to make ATP from ADP and Pi using FADH2 than using NADH. d. FADH2 is made only in the citric acid cycle while NADH is made in glycolysis, acetyl CoA formation, and the citric acid cycle. e. The H+ gradient made from electron transport using NADH is located in a different part of the mitochondrion than the H+ gradient made using FADH2.

b. Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

Which of the following statements about complex II is NOT true? a. Unlike complex I, the transfer of electrons to CoQ does not involve the pumping of protons. b. The complex draws electrons from succinate derived from fatty acid oxidation. c. The electrons flow toward CoQ, just as they do in complex I. d. The electrons pass from FADH2 to Fe+3 to cytochrome b to CoQ.

b. The complex draws electrons from succinate derived from fatty acid oxidation.

Which statement about oxidative phosphorylation is NOT true? a. The overall energy released by the reduction of O2 to water is more than enough to compensate for the large amount of energy required for ATP synthesis. b. The mechanisms of phosphorylation and oxidation are directly coupled. c. The P/O for NADH is ~2.5. d. The P/O for succinate is less than that for NADH, at ~ 1.5.

b. The mechanisms of phosphorylation and oxidation are directly coupled.

Which complexes of the electron transport system carry Fe-S clusters? a. complexes I, III, and V b. complexes I, II, and III c. complexes I and II d. complexes I, II, and IV

b. complexes I, II, and III

Briefly explain your answer. a. ΔG would probably be positive in vivo for an NADH-linked enzyme, because the low NADP+/NADPH concentration ratio would promote the oxidation of GSH to GSSG. b. ΔG would probably be positive in vivo for an NADH-linked enzyme, because the high NAD+/NADH concentration ratio would promote the oxidation of GSH to GSSG. c. ΔG would probably be positive in vivo for an NADPH-linked enzyme, because the low NADP+/NADPH concentration ratio would promote the reduction of GSSG to GSH. d. ΔG would probably be positive in vivo for an NADPH-linked enzyme, because the high NAD+/NADH concentration ratio would promote the reduction of GSSG to GSH.

b. ΔG would probably be positive in vivo for an NADH-linked enzyme, because the high NAD+/NADH concentration ratio would promote the oxidation of GSH to GSSG.

Indicate the probable flow of electrons in this system. a. β−hydroxybutyrate⟶complexI⟶NADH⟶CoQ⟶complexIII⟶cytochromec b. β−hydroxybutyrate⟶NADH⟶complexI⟶CoQ⟶complexIII⟶cytochromec c. β−hydroxybutyrate⟶complexIII⟶NADH⟶complexI⟶CoQ⟶cytochromec d. β−hydroxybutyrate⟶complexI⟶CoQ⟶complexIII⟶NADH⟶cytochromec e. β−hydroxybutyrate⟶CoQ⟶NADH⟶complexI⟶complexIII⟶cytochromec

b. β−hydroxybutyrate⟶NADH⟶complexI⟶CoQ⟶complexIII⟶cytochromec

Write a balanced equation for the overall reaction (including cyt c oxidation and ATP synthesis). a. Cytcox+12O2+ATP+2H+⟶Cytcred+ADP+Pi+2H2O b. 2Cytcred+12O2+2H+⟶2Cytcox+H2O c. 2Cytcred+12O2+ADP+Pi+2H+⟶2Cytcox+ATP+2H2O d. Cytcox+O2+4H+⟶Cytcred+2H2O

c. 2Cytcred+12O2+ADP+Pi+2H+⟶2Cytcox+ATP+2H2O

Arrange the sequence of events for the overall mitochondrial respiratory assembly in the correct order. 1) Coenzyme Q-cytochrome c reductase passes electrons to cytochrome c. 2) Coenzyme Q releases its electrons to complex III. 3) Cytochrome oxidase catalyzes the reduction of O2 to water. 4) Succinate, through complex II, and NADH, via complex I, release electrons to coenzyme Q. a. 4, 1, 2, 3 b. 4, 3, 1, 2 c. 4, 2, 1, 3 d. 4, 1, 3, 2

c. 4, 2, 1, 3

Consider an ATP synthase complex with 12 "c" subunits in its F0 rotor (as illustrated in the molecular model of the E. coli enzyme in section II of the tutorial). How many protons must translocate through the F0 complex in order to generate 10 molecules of ATP? a. 10 b. 12 c. 40 d. 120

c. 40

The rate of cellular respiration is regulated by its major product, ATP, via feedback inhibition. As the diagram shows, high levels of ATP inhibit phosphofructokinase (PFK), an early enzyme in glycolysis. As a result, the rate of cellular respiration, and thus ATP production, decreases. Feedback inhibition enables cells to adjust their rate of cellular respiration to match their demand for ATP. Suppose that a cell's demand for ATP suddenly exceeds its supply of ATP from cellular respiration. a. ATP levels would rise at first, decreasing the inhibition of PFK and increasing the rate of ATP production. b. ATP levels would fall at first, increasing the inhibition of PFK and increasing the rate of ATP production. c. ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production. d. ATP levels would rise at first, increasing the inhibition of PFK and increasing the rate of ATP production.

c. ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.

Years ago there was interest in using uncouplers such as dinitrophenol as weight control agents. Presumably, fat could be oxidized without concomitant ATP synthesis for re-formation of fat or carbohydrate. Why was this a bad (i.e., fatal) idea? a. Because dinitrophenol led to the release of energy which was dissipated as heat, and the subjects developed uncontrollable fevers. b. Because the compounds not used for ATP were dissipated in the body, and the subjects developed uncontrollable fevers. c. Because the energy not used for ATP was dissipated as heat, and the subjects developed uncontrollable fevers. d. Because dinitrophenol led to the release of toxic compounds which were dissipated in the body, and the subjects developed uncontrollable fevers.

c. Because the energy not used for ATP was dissipated as heat, and the subjects developed uncontrollable fevers.

Which of the following is NOT an electron acceptor in the mitochondrial respiratory chain? a. FMN b. Cu2+ c. CoQH2 d. FAD e. Fe3+

c. CoQH2

When pure reduced cytochrome c is added to carefully prepared mitochondria along with ADP, Pi, antimycin A, and oxygen, the cytochrome c becomes oxidized, and ATP is formed, with a P/O ratio approaching 1.0. Indicate the probable flow of electrons in this system. a. Cytc⟶hemea⟶CuA⟶hemea3−CuB⟶O2 b. Cytc⟶hemea3−CuB⟶CuA⟶hemea⟶O2 c. Cytc⟶CuA⟶hemea⟶hemea3−CuB⟶O2 d. Cytc⟶hemea⟶hemea3−CuB⟶CuA⟶O2

c. Cytc⟶CuA⟶hemea⟶hemea3−CuB⟶O2

Which of the following statements is false? a. During electron transport protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space. b. Oxygen is reduced to water at complex IV of the mitochondrial respiratory chain. c. Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane. d. All of the protein complexes of the mitochondrial respiratory chain are bound in the inner mitochondrial membrane. e. The citric acid cycle is linked directly to the mitochondrial respiratory chain at the site of complex II.

c. Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.

Why was cyanide added in this experiment? a. To block cytochrome oxidase and force protons to enter the respiratory chain at cytochrome b. b. To catalyze cytochrome oxidase and force electrons to enter the respiratory chain at cytochrome c. c. To block cytochrome oxidase and force electrons to exit the respiratory chain at cytochrome c. d. To catalyze cytochrome oxidase and force protons to exit the respiratory chain at cytochrome b.

c. To block cytochrome oxidase and force electrons to exit the respiratory chain at cytochrome c.

What is the function of the cyanide? a. To catalyze cytochrome oxidase, so that electrons exit the chain at β-hydroxybutyrate. b. To block cytochrome oxidase, so that protons exit the chain at cytochrome c. c. To block cytochrome oxidase, so that electrons exit the chain at cytochrome c. d. To catalyze cytochrome oxidase, so that protons exit the chain at β-hydroxybutyrate.

c. To block cytochrome oxidase, so that electrons exit the chain at cytochrome c.

Which of the four complexes pump protons out of the mitochondrial matrix? a. complexes I, II, and IV b. complexes I, II, and III c. complexes I, III, and IV d. All four complexes pump protons out of the mitochondrial matrix.

c. complexes I, III, and IV

In the electron transport chain, protons are pumped from where to where in the mitochondria of eukaryotic cells? a. from the intermembrane space to the cytosol b. from the intermembrane space to the matrix c. from the mitochondrial matrix to the intermembrane space d. from the outside of the cell to the cytosol e. from the outside of the cell to the matrix

c. from the mitochondrial matrix to the intermembrane space

To determine whether isolated mitochondria exhibit respiratory control, one determines the ratio of rates of oxygen uptake in two different states. Which states? a. step 4 divided by step 3 b. step 3 divided by step 5 c. step 3 divided by step 4 d. step 5 divided by step 3 e. step 5 divided by step 4 f. step 4 divided by step 5

c. step 3 divided by step 4.

In mitochondrial electron transport, what is the direct role of O2? a. to oxidize NADH and FADH2 from glycolysis, acetyl CoA formation, and the citric acid cycle b. to provide the driving force for the production of a proton gradient c. to function as the final electron acceptor in the electron transport chain d. to provide the driving force for the synthesis of ATP from ADP and Pi

c. to function as the final electron acceptor in the electron transport chain

In the molecular model of the E. coli F0 rotor, the c-ring rotates as a direct result of __________. a. a proton leaving via the exit half-channel b. reprotonation of Asp61 in the C-terminal helix of a "c" subunit c. twisting of the C-terminal helix in a "c" subunit upon deprotonation Asp61. d. deprotonation of Arg 210 on the "a" subunit.

c. twisting of the C-terminal helix in a "c" subunit upon deprotonation Asp61.

Metabolism can be bisected into two subcategories: catabolism and anabolism. _______ takes complex organic molecules and breaks them down into simpler molecules; this is often accompanied by the __________ of energy. _______ builds up biomolecules from simpler substances; this is often accompanied by the __________ of energy. Both pathways use simple two-carbon organic molecules (such as _______) as common intermediates. These intermediates can then enter the _______, where they are further _______ to generate carbon dioxide and _______ electron carriers, along with small amounts of ATP. THe electrons on these carriers are finally sent through the _______ to create a proton (H+) gradient. Release of this proton gradient results in the generation of _______. options: ATP citric acid cycle an amino acid consumption glucose oxidized electron transport chain glycolysis anabolism acetyl-CoA catabolism release hydrolized reduced

catabolism; release; anabolism; consumption acetyl-CoA; citric acid cycle; oxidized; reduced; electron transport chain; ATP

Which of the following statements about oxidative phosphorylation by ATP synthase is FALSE? a. Inhibitors disrupt electron flow as well as ATP synthesis. b. Uncouplers dissipate the electrochemical gradient but electron transport continues without ATP production. c. The electrochemical gradient across the inner mitochondrial membrane generated by electron flow is used to synthesize ATP. d. A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP. e. ATP synthesis occurs via simultaneous conformational changes in protein subunits containing catalytic sites.

d. A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP.

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions? a. The change in the solution's pH results in a gradient across the chloroplast membranes such that there is a lower concentration of protons inside the vesicles and a higher concentration outside. b. ATP will be produced because the proton gradient favors proton movement through the ATP synthase channels. c. Protons will not diffuse toward the outside of the vesicles. d. ATP will not be produced because there is no ADP and inorganic phosphate in the solution.

d. ATP will not be produced because there is no ADP and inorganic phosphate in the solution.

Which of the following are part of the chemiosmotic coupling model? 1) Protons are pumped out of the mitochondrial matrix into the intermembrane space. 2) The active transport of protons is driven by the free energy derived from electron transport. 3) Increasing the concentration of protons on the other side of the inner membrane creates a charge and a pH imbalance that releases energy upon proton flow back into the matrix. 4) The energy released by the return of protons to the matrix is what drives ATP synthesis. a. Only statements 2, 3, and 4 are correct. b. Only statements 1, 2, and 4 are correct. c. Only statements 1, 2, and 3 are correct. d. All of the listed choices are correct.

d. All of the listed choices are correct.

List the sequence of electron carriers in this system. a. Succinate⟶Q⟶FAD⟶cytb⟶cytc1⟶cytc b. Succinate⟶Q⟶cytb⟶FAD⟶cytc1⟶cytc c. Succinate⟶cytc1⟶Q⟶FAD⟶cytb⟶cytc d. Succinate⟶FAD⟶Q⟶cytb⟶cytc1⟶cytc e. Succinate⟶cytb⟶FAD⟶Q⟶cytc1⟶cytc f. Succinate⟶cytc1⟶FAD⟶Q⟶cytb⟶cytc

d. Succinate⟶FAD⟶Q⟶cytb⟶cytc1⟶cytc

Why was antimycin A added? a. To catalyze oxidation of endogenous substrates and to inhibit reverse proton flow (i.e., to prevent protons flowing back up the respiratory chain). b. To block reduction of endogenous substrates and to inhibit reverse electron flow (i.e., to prevent electrons flowing back up the respiratory chain). c. To catalyze reduction of endogenous substrates and to inhibit reverse proton flow (i.e., to prevent protons flowing back up the respiratory chain). d. To block oxidation of endogenous substrates and to inhibit reverse electron flow (i.e., to prevent electrons flowing back up the respiratory chain).

d. To block oxidation of endogenous substrates and to inhibit reverse electron flow (i.e., to prevent electrons flowing back up the respiratory chain).

Which state probably predominates in resting skeletal muscle of a well-nourished animal? a. state 1 b. state 2 c. state 3 d. state 4 e. state 5

d. state 4 (ADP level is low because ATP level is high)

Write a balanced equation for the overall reaction occurring in this system, showing oxidation of the initial electron donor, reduction of the final acceptor, and synthesis of ATP. a. fumarate+cytcox+ADP+Pi⟶succinate+cytcred+ATP+H2O b. fumarate+2cytcred+ADP+Pi⟶succinate+2cytcox+ATP+H2O c. succinate+cytcox+ADP⟶fumarate+cytcred+ATP+Pi+H2O d. succinate+2cytcox+ADP+Pi⟶fumarate+2cytcred+ATP+H2O e. succinate+2cytcred+ADP⟶fumarate+2cytcox+ATP+Pi+H2O

d. succinate+2cytcox+ADP+Pi⟶fumarate+2cytcred+ATP+H2O

The rotation of the F0 rotor is driven by the proton gradient. Examine the F0 rotor of E. coli. The protons enter through the entry half-channel and are passed on to a(n) __________. a. Arg residue on the "a" subunit's helix closest to the c-ring b. protonated Asp residue on one "c" subunit's C-terminal helix c. Arg residue on one "c" subunit's C-terminal helix d. unprotonated Asp residue on one "c" subunit's C-terminal helix

d. unprotonated Asp residue on one "c" subunit's C-terminal helix

Write a balanced equation for the overall reaction occurring in this system (electron transport and ATP synthesis). a. acetoacetate+2cytcred+2ADP+2Pi+4H+⟶β−hydroxybutyrate+2cytcox+2ATP+2H2O b. acetoacetate+2cytcox+2ATP+2H+⟶β−hydroxybutyrate+2cytcred+2ADP+2Pi+H2O c. β−hydroxybutyrate+cytcred+2ATP+4H+⟶acetoacetate+cytcox+2ADP+2Pi+2H2O d. β−hydroxybutyrate+2cytcox+2ADP+2Pi+4H+⟶acetoacetate+2cytcred+2ATP+2H2O

d. β−hydroxybutyrate+2cytcox+2ADP+2Pi+4H+⟶acetoacetate+2cytcred+2ATP+2H2O

The redox potential of the flavin, which _________ from its ____________, depends on its ___________ environment. In lipoamide dehydrogenase, its redox potential is held more _________ than in other flavin dehydrogenases, so that _________ can be passed onto _____________ under physiological conditions. options: lipids does not dissociate enzyme NADP+ positive carbohydrate NAD+ protein substrate electrons protons negative dissociates

does not dissociate; enzyme; protein negative; electrons; NAD+

Which state probably predominates in vivo in skeletal muscle fatigued from a long and strenuous workout? a. state 1 b. state 2 c. state 3 d. state 4 e. state 5

e. state 5 (where O2 is depleted)

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

photophosphorylation

Sort the following protein complexes of the electron transport chain according to whether they are involved in pumping protons across the inner mitochondrial membrane or not. options: cytochrome c, complex I, complex III, complex II, complex IV, coenzyme Q bins: pumps protons or does not pump protons

pumps protons: complex I, complex III, complex IV does not pump protons: cytochrome C, coenzyme Q, complex II