Question 1

Which statement is FALSE regarding ATP synthase?

Accepted Answer

A)  The active site contains multiple positive charges that interact with the substrates. 
B)  The energy difference between bound substrate and bound product is close to zero. 
C)  As an enzyme, ATP synthase is classified as a hydrolase. 
D)  ATP synthase can be classified as a primary active transporter. 
E)  ADP binds more tightly to the active site than ATP.

Question 2

In his studies of alcoholic fermentation by yeast, Louis Pasteur noted that the sudden addition of oxygen (O₂) to a previously anaerobic culture of fermenting grape juice resulted in a dramatic decrease in the rate of glucose consumption. This "Pasteur effect" can be counteracted by the addition of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. (a) Why would the yeast cells consume less glucose in the presence of oxygen? Can you estimate how much less glucose they would use? (b) Why would DNP counteract or prevent the Pasteur effect?

Accepted Answer

The answer of In his studies of alcoholic fermentation by...

Question 3

The consumption of acetyl-CoA by the citric acid cycle is DECREASED under which condition?

Accepted Answer

A)  the concentration of NAD+ being high 
B)  the concentration of oxaloacetate being high 
C)  NADH being rapidly re-oxidized via the electron-transport chain 
D)  the mitochondrial ATP synthase being inactive 
E)  the concentration of both NAD+ and oxaloacetate being high

Question 4

Which step is NOT part of the proton-translocation process in ATP synthase?

Accepted Answer

A)  A negatively charged amino acid in each c subunit becomes neutral upon proton binding. 
B)  A positively charged amino acid in the a subunit forms an ion pair with a charged amino acid in a c subunit. 
C)  Deprotonated c subunits are able to interact only with the a subunit. 
D)  An arginine in the a subunit is reversibly protonated and deprotonated in each proton binding event. 
E)  Proton direction is determined by the relative concentrations of protons on either side of the membrane.

Question 5

Which statement about human mitochondria is TRUE?

Accepted Answer

A)  About 900 mitochondrial proteins are encoded by nuclear genes. 
B)  Mitochondrial genes are inherited from both maternal and paternal sources. 
C)  rRNA and tRNA are imported from the cytoplasm and used in mitochondrial protein synthesis. 
D)  The mitochondrial genome codes for all proteins found in mitochondria. 
E)  The mitochondrial genome is not subject to mutations.

Question 6

Which factor is NOT controlled by hypoxia-inducible factor (HIF-1)?

Accepted Answer

A)  glucose transport 
B)  glycolysis 
C)  citric acid cycle 
D)  Compex I of the respiratory chain 
E)  Complex IV of the respiratory chain

Question 7

Consider a liver cell carrying out the oxidation of glucose under aerobic conditions. Suppose that we added a very potent and specific inhibitor of the mitochondrial ATP synthase, completely inhibiting this enzyme. Indicate whether each of the following statements about the effect of this inhibitor is true or false; if false, explain in a sentence or two why it is false.
____ (a) ATP production in the cell will quickly drop to zero.
____ (b) The rate of glucose consumption by this cell will decrease sharply.
____ (c) The rate of oxygen consumption will increase.
____ (d) The citric acid cycle will speed up to compensate.
____ (e) The cell will switch to fatty acid oxidation as an alternative to glucose oxidation, and the inhibitor will therefore have no effect on ATP production.

Accepted Answer

The answer of Consider a liver cell carrying out the...

Question 8

Which phrase BEST describes the role of mitochondria in apoptosis?

Accepted Answer

A)  escape of cytochrome c into the cytoplasm 
B)  increased rate of fatty acid $\beta$ oxidation 
C)  an increase in permeability of outer membrane 
D)  uncoupling of oxidative phosphorylation 
E)  both escape of cytochrome c into the cytoplasm and an increase in permeability of outer membrane

Question 9

Which statement about the chemiosmotic theory is CORRECT?

Accepted Answer

A)  Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. 
B)  It predicts that oxidative phosphorylation can occur, even in the absence of an intact inner mitochondrial membrance. 
C)  The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes. 
D)  The membrane ATP synthase has no significant role in the chemiosmotic theory. 
E)  All of the statements are correct.

Question 10

Coenzyme Q is a prosthetic group for which of the following complexes in the electron transport chain?

Accepted Answer

A)  Complex I 
B)  Complex II 
C)  Complex III 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 11

For mitochondria where an uncoupler for oxidative phosphorylation is present, which statement is TRUE?

Accepted Answer

A)  The rate of NADH reoxidation will decrease relative to coupled mitochondria. 
B)  The citric acid cycle will be inhibited relative to uncoupled mitochondria. 
C)  The P:O ratio for FADH2 will increase relative to uncoupled mitochondria. 
D)  The amount of ATP generated from FADH2 will be less than the amount of ATP generated from NADH. 
E)  None of the statements is true.

Question 12

Cyanide ion (CN^-) blocks electron transfer in mitochondria at the level of cytochrome a + a₃. 2,4-Dinitrophenol (DNP) is an uncoupler of mitochondrial oxidative phosphorylation. Draw graphs (ATP synthesized vs. time and O₂ consumed vs. time) with labeled curves to show the effects of adding each of these compounds separately to a suspension of mitochondria supplied with O₂, succinate, ADP, and P_i. Use an arrow to indicate the time of drug addition.

Accepted Answer

The answer of Cyanide ion (CN^-) blocks electron transfer in...

Question 13

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Accepted Answer

The answer of When the F₁ portion of the ATP...

Question 14

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

Accepted Answer

The answer of Describe and explain the two different ratios...

Question 15

Which complex in the electron-transport chain contains copper ions?

Accepted Answer

A)  Complex I 
B)  Complex II 
C)  Complex III 
D)  Complex IV 
E)  None of these complexes contains copper ions.

Question 16

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

Accepted Answer

A)  glycolysis. 
B)  oxidative phosphorylation. 
C)  pyruvate oxidation. 
D)  the citric acid cycle. 
E)  All of the answers are correct.

Question 17

Which statement is FALSE regarding flavoproteins?

Accepted Answer

A)  They may contain either FMN or FAD. 
B)  The reduction potential of the flavin will depend on the amino acids in the polypeptide chain. 
C)  They will need at least two substrates in order to function as enzymes. 
D)  They are always integral membrane proteins. 
E)  Most flavoproteins in electron transport have a lower reduction potential than coenzyme Q.

Question 18

Complex III contains which cofactor as a prosthetic group?

Accepted Answer

A)  iron-sulfur clusters 
B)  FAD 
C)  FMN 
D)  coenzyme Q 
E)  copper

Question 19

Which statement about the chemiosmotic theory is FALSE?

Accepted Answer

A)  Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane. 
B)  Energy is conserved as a transmembrane pH gradient. 
C)  Oxidative phosphorylation cannot occur in membrane-free preparations. 
D)  The effect of uncoupling reagents is a consequence of their ability to carry protons through membranes. 
E)  The membrane ATPase, which plays an important role in other hypotheses for energy coupling, has no significant role in the chemiosmotic theory.

Question 20

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.

Accepted Answer

The answer of Mitochondria carrying out oxidative phosphorylation consume oxygen....

Exam 19: Oxidative Phosphorylation and Photophosphorylation

Which statement is FALSE regarding ATP synthase?

The consumption of acetyl-CoA by the citric acid cycle is DECREASED under which condition?

Which step is NOT part of the proton-translocation process in ATP synthase?

Which statement about human mitochondria is TRUE?

Which factor is NOT controlled by hypoxia-inducible factor (HIF-1) ?

Which phrase BEST describes the role of mitochondria in apoptosis?

Which statement about the chemiosmotic theory is CORRECT?

Coenzyme Q is a prosthetic group for which of the following complexes in the electron transport chain?

For mitochondria where an uncoupler for oxidative phosphorylation is present, which statement is TRUE?

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

Which complex in the electron-transport chain contains copper ions?

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

Which statement is FALSE regarding flavoproteins?

Complex III contains which cofactor as a prosthetic group?

Which statement about the chemiosmotic theory is FALSE?

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.

Exam 19: Oxidative Phosphorylation and Photophosphorylation

Which statement is FALSE regarding ATP synthase?

The consumption of acetyl-CoA by the citric acid cycle is DECREASED under which condition?

Which step is NOT part of the proton-translocation process in ATP synthase?

Which statement about human mitochondria is TRUE?

Which factor is NOT controlled by hypoxia-inducible factor (HIF-1) ?

Which phrase BEST describes the role of mitochondria in apoptosis?

Which statement about the chemiosmotic theory is CORRECT?

Coenzyme Q is a prosthetic group for which of the following complexes in the electron transport chain?

For mitochondria where an uncoupler for oxidative phosphorylation is present, which statement is TRUE?

When the F1 portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Describe and explain the two different ratios that affect the rate of respiration in mitochondria. What is accomplished by these control mechanisms?

Which complex in the electron-transport chain contains copper ions?

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

Which statement is FALSE regarding flavoproteins?

Complex III contains which cofactor as a prosthetic group?

Which statement about the chemiosmotic theory is FALSE?

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and Pi.

When the F₁ portion of the ATP synthetase complex is removed from the mitochondrial membrane and studied in solution, it functions as an ATPase. Why does it not function as an ATP synthetase?

Mitochondria carrying out oxidative phosphorylation consume oxygen. Explain what happens to this oxygen, and describe the effect of an uncoupling agent such as 2,4-dinitrophenol on the rate of oxygen consumption. Assume there is a sufficient supply of oxidizable substrate, ADP, and P_i.