Question 1

Upon the addition of 2,4-dinitrophenol (DNP)to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate,all of the following occur except:

Accepted Answer

DNP acts as an uncoupler of oxidative phosphorylation, which increases oxygen consumption (B), decreases the P/O ratio to 0 (C), dissipates the proton gradient (D), and maximizes electron transport rate (E). However, it does not decrease oxygen consumption (A).

Question 2

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 of the following would be found in the oxidized state?

Accepted Answer

B

Question 3

Which of the following statements about the chemiosmotic theory is correct?

Accepted Answer

The chemiosmotic theory proposes that electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. This gradient of protons creates a proton motive force, which is used by ATP synthase to produce ATP through oxidative phosphorylation. Therefore, statement A is correct. Statements B, C, and D are incorrect as they do not accurately reflect the chemiosmotic theory.

Question 4

In normal mitochondria,the rate of NADH consumption (oxidation)will:

Accepted Answer

In normal mitochondria, NADH consumption is linked to ATP production. A) Active muscles require more ATP, increasing NADH oxidation. B) Inhibition of ATP synthase reduces NADH oxidation, but uncouplers increase it by dissipating the proton gradient. C) Without ADP, ATP synthesis halts, reducing NADH oxidation. D) Cyanide blocks electron transfer, stopping NADH oxidation.

Question 5

Cyanide,oligomycin,and 2,4-dinitrophenol (DNP)are inhibitors of mitochondrial aerobic phosphorylation.Which of the following statements correctly describes the mode of action of the three inhibitors?

Accepted Answer

The answer of Cyanide,oligomycin,and 2,4-dinitrophenol (DNP)are inhibitors of mitochondrial aerobic...

Question 6

Which of the following statements about energy conservation in the mitochondrion is false?

Accepted Answer

Uncouplers and inhibitors have opposite effects on electron transfer. Uncouplers increase the flow of electrons down the chain of carriers by dissipating the proton motive force as heat, while inhibitors block electron transfer to oxygen. Therefore, (D) is the false statement, as it incorrectly suggests that uncouplers have the same effect as inhibitors.

Question 7

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:

Accepted Answer

Cytochrome c is a one-electron acceptor, whereas QH₂ (a quinol, such as ubiquinol) is a two-electron donor. This means that for each molecule of QH₂ oxidized, two molecules of cytochrome c are required to accept the two electrons.

Question 8

Which of the following electron carriers is not able to transfer one electron at a time?

Accepted Answer

The answer of Which of the following electron carriers is...

Question 9

Which of the following statements about the chemiosmotic theory is false?

Accepted Answer

The statement that the membrane ATPase has no significant role in the chemiosmotic theory is false. In fact, the ATPase is the key enzyme responsible for synthesizing ATP from ADP and Pi using the energy stored in the transmembrane pH gradient. This is a central component of the chemiosmotic theory.

Question 10

Which of the following is not true of the proton motive force (pmf)?

Accepted Answer

The generation of the proton motive force in mitochondria does not require succinate. Succinate is a substrate that enters the Krebs cycle, which is involved in the generation of reducing equivalents that feed into the electron transport chain to generate the proton motive force.

Question 11

Which of the following is correct concerning the mitochondrial ATP synthase?

Accepted Answer

The mitochondrial ATP synthase catalyzes ATP synthesis with a ΔG'° close to zero due to the proton gradient across the mitochondrial membrane, which provides the necessary energy.

Question 12

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:

Accepted Answer

The answer of The oxidation of a particular hydroxy substrate...

Question 13

During oxidative phosphorylation,the proton motive force that is generated by electron transport is used to:

Accepted Answer

The proton motive force generated by electron transport induces a conformational change in the ATP synthase, allowing it to bind ADP and Pi and generate ATP.

Question 14

Almost all of the oxygen (O₂)one consumes in breathing is converted to:

Accepted Answer

Oxygen consumed in breathing is primarily used in the electron transport chain during cellular respiration, where it acts as the final electron acceptor and is converted to water.

Question 15

The rate of oxidative phosphorylation in mitochondria is controlled primarily by:

Accepted Answer

The answer of The rate of oxidative phosphorylation in mitochondria...

Question 16

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?

Accepted Answer

The rapid uptake of coenzyme Z by mitochondria does not necessarily indicate its role in the electron transport chain, as it could be due to other factors such as non-specific binding or transport mechanisms unrelated to electron transfer.

Question 17

Which of the following is not a feature of complex IV?

Accepted Answer

The answer of Which of the following is not a...

Question 18

Reduced QH₂ is not formed by which of the following?

Accepted Answer

Complex III and cytochrome c do not form reduced QH2; instead, they are involved in the transfer of electrons from reduced QH2 to cytochrome c in the electron transport chain.

Question 19

When the $\Delta$ G'° 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:

Accepted Answer

The fact that the F1F1F1S1F1F1F10G'° of the ATP synthesis reaction is close to zero on the surface of the ATP synthase enzyme suggests that the enzyme is stabilizing ATP relative to ADP, thus making it easier for the reaction to occur. This is because ATP synthase catalyzes the conversion of ADP to ATP and stabilizes the ADP and inorganic phosphate during the process of ATP synthesis. Therefore, choice D is the best option.

Question 20

The relative concentrations of ATP and ADP control the cellular rates of:

Accepted Answer

The relative concentrations of ATP and ADP regulate the rates of glycolysis, oxidative phosphorylation, pyruvate oxidation, and the citric acid cycle, as these processes are all involved in energy production and are sensitive to the energy needs of the cell.

Quiz 19: Oxidative Phosphorylation and Photophosphorylation

Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate,all of the following occur except:

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 of the following would be found in the oxidized state?

Which of the following statements about the chemiosmotic theory is correct?

In normal mitochondria,the rate of NADH consumption (oxidation) will:

Cyanide,oligomycin,and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation.Which of the following statements correctly describes the mode of action of the three inhibitors?

Which of the following statements about energy conservation in the mitochondrion is false?

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:

Which of the following electron carriers is not able to transfer one electron at a time?

Which of the following statements about the chemiosmotic theory is false?

Which of the following is not true of the proton motive force (pmf) ?

Which of the following is correct concerning the mitochondrial ATP synthase?

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:

During oxidative phosphorylation,the proton motive force that is generated by electron transport is used to:

Almost all of the oxygen (O₂) one consumes in breathing is converted to:

The rate of oxidative phosphorylation in mitochondria is controlled primarily by:

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?

Which of the following is not a feature of complex IV?

Reduced QH₂ is not formed by which of the following?

When the $\Delta$ G'° 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:

The relative concentrations of ATP and ADP control the cellular rates of:

Quiz 19: Oxidative Phosphorylation and Photophosphorylation

Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate,all of the following occur except:

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 of the following would be found in the oxidized state?

Which of the following statements about the chemiosmotic theory is correct?

In normal mitochondria,the rate of NADH consumption (oxidation) will:

Cyanide,oligomycin,and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation.Which of the following statements correctly describes the mode of action of the three inhibitors?

Which of the following statements about energy conservation in the mitochondrion is false?

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:

Which of the following electron carriers is not able to transfer one electron at a time?

Which of the following statements about the chemiosmotic theory is false?

Which of the following is not true of the proton motive force (pmf) ?

Which of the following is correct concerning the mitochondrial ATP synthase?

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:

During oxidative phosphorylation,the proton motive force that is generated by electron transport is used to:

Almost all of the oxygen (O2) one consumes in breathing is converted to:

The rate of oxidative phosphorylation in mitochondria is controlled primarily by:

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?

Which of the following is not a feature of complex IV?

Reduced QH2 is not formed by which of the following?

When the Δ\DeltaΔ G'° 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:

The relative concentrations of ATP and ADP control the cellular rates of:

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 of the following would be found in the oxidized state?

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:

Almost all of the oxygen (O₂) one consumes in breathing is converted to:

Reduced QH₂ is not formed by which of the following?

When the $\Delta$ G'° 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: