Question 1

Which molecule can reduce the proton gradient in mitochondria?

Accepted Answer

A)   Pi-H+ symporter
B)   ATP synthase
C)   pyruvate translocase
D)   All of the answers are correct.
E)   None of the answers is correct.F) None of the above
G) C) and E)

Question 2

Describe, in simple diagrams and a few words, the chemiosmotic theory for coupling oxidation to phosphorylation in mitochondria.

Accepted Answer

The chemiosmotic theory explains how the...

Question 3

What mechanism accounts for mitochondrial inheritance in sexual reproduction in animals?

Accepted Answer

A)   Male gametes do not contain mitochondria.
B)   Mitochondria from male gametes do not enter the ovum.
C)   Female mitochondria are able to outcompete male mitochondria.
D)   Male mitochondria are degraded after fertilization.
E)   Male and female mitochondria merge after fertilization to form hybrids.F) A) and C)
G) B) and E)

Question 4

How do the cytosolic and mitochondrial isozymes of glycerol 3-phosphate dehydrogenase differ from each other?

Accepted Answer

Glycerol 3-phosphate dehydrogenase (GPDH) is an enzyme that catalyzes the reversible redox conversion of dihydroxyacetone phosphate (DHAP) to glycerol 3-phosphate (G3P). There are two distinct isozymes of GPDH: one located in the cytosol (cGPDH) and the other in the mitochondria (mGPDH). These isozymes differ in several key aspects:

1. **Location and Function in Cellular Metabolism**:
   - **Cytosolic GPDH (cGPDH)**: This isozyme is involved in the glycolytic pathway, where it facilitates the conversion of DHAP to G3P, which can then be used for triglyceride synthesis or further glycolysis. It plays a role in the shuttle mechanism for transferring reducing equivalents from NADH produced in the cytosol into the mitochondria.
   - **Mitochondrial GPDH (mGPDH)**: This isozyme is part of the glycerol phosphate shuttle, which transfers reducing equivalents from cytosolic NADH into the electron transport chain within the mitochondria. mGPDH oxidizes G3P back to DHAP while reducing FAD to FADH2, which then donates electrons to the respiratory chain.

2. **Enzymatic Mechanism and Electron Carriers**:
   - **cGPDH** uses NAD+/NADH as its electron acceptors and donors.
   - **mGPDH** uses FAD/FADH2 as its electron acceptors and donors.

3. **Genetic Origin and Regulation**:
   - **cGPDH** and **mGPDH** are encoded by different genes and are subject to different regulatory mechanisms. cGPDH is typically regulated by the availability of substrates and by the energy needs of the cell, while mGPDH is regulated in part by the redox state of the mitochondrial matrix and the demand for ATP production.

4. **Physiological Role**:
   - **cGPDH** is primarily involved in lipid metabolism and the regulation of glycolysis.
   - **mGPDH** is crucial for the efficient transfer of electrons from cytosolic NADH into the mitochondrial electron transport chain, which is essential for ATP production during oxidative phosphorylation.

5. **Tissue Distribution**:
   - The expression of **cGPDH** and **mGPDH** can vary between tissues, depending on the metabolic requirements of the cells. For example, tissues with high rates of fatty acid synthesis (like liver and adipose tissue) have higher levels of cGPDH.

6. **Kinetic Properties**:
   - The kinetic properties of cGPDH and mGPDH, such as their affinity for substrates and sensitivity to inhibitors, can differ, reflecting their adaptation to specific cellular roles and conditions.

In summary, the cytosolic and mitochondrial isozymes of glycerol 3-phosphate dehydrogenase differ in their cellular location, function, enzymatic mechanisms, genetic regulation, physiological roles, tissue distribution, and kinetic properties. These differences allow them to fulfill distinct roles in cellular metabolism, particularly in the context of lipid metabolism and energy production.

Question 5

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

Accepted Answer

A)   NADH
B)   FMN
C)   FAD
D)   ubiquinone
E)   hemeF) D) and E)
G) A) and E)

Question 6

When the $\Delta$G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Accepted Answer

The Gibbs free energy change (ΔG'°) of a...

Question 7

Upon the addition of 2,4-dinitrophenol (DNP)  to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate, what does NOT occur?

Accepted Answer

A)   Oxygen consumption decreases.
B)   Oxygen consumption increases.
C)   The P/O ratio drops from a value of approximately 2.5 to 0.
D)   The proton gradient dissipates.
E)   The rate of transport of electrons from NADH to O2 becomes maximal.F) A) and B)
G) B) and D) A

Question 8

Which cofactor is MOST commonly involved as a cosubstrate in catabolic reactions where a metabolite is oxidized?

Accepted Answer

A)   NAD+
B)   FAD
C)   NADPH
D)   NADH
E)   coenzyme QF) C) and E)
G) B) and D)

Question 9

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

Accepted Answer

Hypoxia-inducible factor 1 (HIF-1) is a ...

Question 10

Mutations in mitochondrial genes do NOT play a role in:

Accepted Answer

A)   adult onset diabetes.
B)   cystic fibrosis.
C)   hypertrophic cardiomyopathy.
D)   Leber's hereditary optic neuropathy.
E)   myoclonic epilepsy.F) D) and E)
G) A) and C)

Question 11

Which statement is TRUE regarding the reduction potential of mitochondrial glycerol 3 phosphate dehydrogenase?

Accepted Answer

A)   It will be higher than those of both NADH and Complex III.
B)   It will be lower than those of both NADH and Complex III.
C)   It will be higher than that of NADH but lower than that of Complex III.
D)   It will be lower than that of NADH but higher than that of Complex III.
E)   No conclusion can be drawn regarding its reduction potential.F) A) and B)
G) None of the above

Question 12

Which statement is NOT a feature of Complex IV?

Accepted Answer

A)   Cytochrome c is a one-electron donor.
B)   Oxygen is a substrate.
C)   Copper is an essential metal for the reaction.
D)   For every electron passed to Complex IV, two protons are consumed from the matrix (N)  side.
E)   In order to generate two water molecules, Complex IV must go through the catalytic cycle two times.F) B) and E)
G) C) and D) E

Question 13

Which statement is TRUE regarding the gamma ( γ\gammaγ )  subunit of ATP synthase?

Accepted Answer

A)   It contains mostly  α\alphaα -helical regular secondary structure.
B)   It exists as a dimer in the F1 portion of ATP synthase.
C)   It prevents the F1 portion from rotating relative to the FO portion.
D)   It interacts with the a and b subunits of the FO portion.
E)   It binds protons as part of the proton translocation process. F) A) and E)
G) A) and B)

Question 14

The ATP synthase F1 portion contains many subunits arranged in a cyclic pattern, yet we cannot really describe it as having cyclic symmetry. Why?

Accepted Answer

ATP synthase is a complex enzyme that pl...

Question 15

Which statement regarding oxidative phosphorylation is TRUE?

Accepted Answer

A)   The rate of electron transport is independent of the magnitude of the proton electrochemical gradient.
B)   ATP synthase utilizes oxidized cofactors.
C)   Proton transfer through the Fo subunit of ATP synthase is required in order for ATP synthesis to occur.
D)   The addition of an uncoupler decreases the rate of re-oxidation of NADH and FADH2, therefore decreasing the rate of the citric acid cycle.
E)   All of the statements are true.F) C) and D)
G) B) and D)

Question 16

Which statement is CORRECT concerning the mitochondrial ATP synthase?

Accepted Answer

A)   It can synthesize ATP after it is extracted from broken mitochondria.
B)   It catalyzes the formation of ATP even though the reaction has a large positive  Δ\DeltaΔ G'°.
C)   It consists of Fo and F1 subunits, which are transmembrane (integral)  polypeptides.
D)   It is actually an ATPase and only catalyzes the hydrolysis of ATP.
E)   When it catalyzes the ATP synthesis reaction, the  Δ\DeltaΔ G'° is actually close to zero. F) A) and B)
G) D) and E)

Question 17

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each:
(1) NADH
(2) Inorganic phosphate
(3) ADP

Accepted Answer

(1) NADH is transported into the mitocho...

Question 18

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

Accepted Answer

The current model for how the proton mot...

Question 19

In which pairing are both transporters symports?

Accepted Answer

A)   adenine nucleotide translocase and phosphate translocase
B)   phosphate translocase and pyruvate translocase
C)   pyruvate translocase and adenine nucleotide translocase
D)   adenine nucleotide translocase and glutamate-aspartate transporter
E)   glutamate-aspartate transporter and phosphate translocaseF) All of the above
G) A) and B)

Question 20

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

Accepted Answer

1) Genetic evidence: Mitochondria have t...

Exam 19: Oxidative Phosphorylation and Photophosphorylation

Which molecule can reduce the proton gradient in mitochondria?

Correct Answer
verified

Describe, in simple diagrams and a few words, the chemiosmotic theory for coupling oxidation to phosphorylation in mitochondria.

Correct Answer
Answered by ExamLex AI
The chemiosmotic theory explains how the...
View Answer

What mechanism accounts for mitochondrial inheritance in sexual reproduction in animals?

Correct Answer
verified

How do the cytosolic and mitochondrial isozymes of glycerol 3-phosphate dehydrogenase differ from each other?

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

Correct Answer
verified

When the $\Delta$ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Correct Answer
Answered by ExamLex AI
The Gibbs free energy change (ΔG'°) of a...
View Answer

Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate, what does NOT occur?

Correct Answer
verified
A

Which cofactor is MOST commonly involved as a cosubstrate in catabolic reactions where a metabolite is oxidized?

Correct Answer
verified

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

Correct Answer
Answered by ExamLex AI
Hypoxia-inducible factor 1 (HIF-1) is a ...
View Answer

Mutations in mitochondrial genes do NOT play a role in:

Correct Answer
verified

Which statement is TRUE regarding the reduction potential of mitochondrial glycerol 3 phosphate dehydrogenase?

Correct Answer
verified

Which statement is NOT a feature of Complex IV?

Correct Answer
verified
E

Which statement is TRUE regarding the gamma ( $\gamma$ ) subunit of ATP synthase?

Correct Answer
verified

The ATP synthase F₁ portion contains many subunits arranged in a cyclic pattern, yet we cannot really describe it as having cyclic symmetry. Why?

Correct Answer
Answered by ExamLex AI
ATP synthase is a complex enzyme that pl...
View Answer

Which statement regarding oxidative phosphorylation is TRUE?

Correct Answer
verified

Which statement is CORRECT concerning the mitochondrial ATP synthase?

Correct Answer
verified

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each: (1) NADH (2) Inorganic phosphate (3) ADP

Correct Answer
Answered by ExamLex AI
(1) NADH is transported into the mitocho...
View Answer

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

Correct Answer
Answered by ExamLex AI
The current model for how the proton mot...
View Answer

In which pairing are both transporters symports?

Correct Answer
verified

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

Correct Answer
Answered by ExamLex AI
1) Genetic evidence: Mitochondria have t...
View Answer

Exam 19: Oxidative Phosphorylation and Photophosphorylation

Which molecule can reduce the proton gradient in mitochondria?

Correct AnswerverifiedShow Answer

Describe, in simple diagrams and a few words, the chemiosmotic theory for coupling oxidation to phosphorylation in mitochondria.

Correct AnswerAnswered by ExamLex AIThe chemiosmotic theory explains how the...View AnswerShow Answer

What mechanism accounts for mitochondrial inheritance in sexual reproduction in animals?

Correct AnswerverifiedShow Answer

How do the cytosolic and mitochondrial isozymes of glycerol 3-phosphate dehydrogenase differ from each other?

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

Correct AnswerverifiedShow Answer

When the Δ\DeltaΔ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Correct AnswerAnswered by ExamLex AIThe Gibbs free energy change (ΔG'°) of a...View AnswerShow Answer

Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate, what does NOT occur?

Correct AnswerverifiedA

Which cofactor is MOST commonly involved as a cosubstrate in catabolic reactions where a metabolite is oxidized?

Correct AnswerverifiedShow Answer

Describe the role of hypoxia-inducible factor (HIF-1) in reducing reactive oxygen species (ROS).

Correct AnswerAnswered by ExamLex AIHypoxia-inducible factor 1 (HIF-1) is a ...View AnswerShow Answer

Mutations in mitochondrial genes do NOT play a role in:

Correct AnswerverifiedShow Answer

Which statement is TRUE regarding the reduction potential of mitochondrial glycerol 3 phosphate dehydrogenase?

Correct AnswerverifiedShow Answer

Which statement is NOT a feature of Complex IV?

Correct AnswerverifiedE

Which statement is TRUE regarding the gamma ( γ\gammaγ ) subunit of ATP synthase?

Correct AnswerverifiedShow Answer

The ATP synthase F1 portion contains many subunits arranged in a cyclic pattern, yet we cannot really describe it as having cyclic symmetry. Why?

Correct AnswerAnswered by ExamLex AIATP synthase is a complex enzyme that pl...View AnswerShow Answer

Which statement regarding oxidative phosphorylation is TRUE?

Correct AnswerverifiedShow Answer

Which statement is CORRECT concerning the mitochondrial ATP synthase?

Correct AnswerverifiedShow Answer

For each of the following explain whether they are transported into or out of the mitochondrion and comment briefly on the mechanism for each: (1) NADH (2) Inorganic phosphate (3) ADP

Correct AnswerAnswered by ExamLex AI(1) NADH is transported into the mitocho...View AnswerShow Answer

Explain briefly the current model for how the proton motive force that is generated by electron transport is used to drive the ATP synthesis reaction.

Correct AnswerAnswered by ExamLex AIThe current model for how the proton mot...View AnswerShow Answer

In which pairing are both transporters symports?

Correct AnswerverifiedShow Answer

Discuss three lines of evidence that support the theory that mitochondria evolved from endosymbiontic bacteria.

Correct AnswerAnswered by ExamLex AI1) Genetic evidence: Mitochondria have t...View AnswerShow Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The chemiosmotic theory explains how the...
View Answer

Correct Answer
verified

Correct Answer
verified

When the $\Delta$ G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it was found to be close to zero. Describe briefly why this is so.

Correct Answer
Answered by ExamLex AI
The Gibbs free energy change (ΔG'°) of a...
View Answer

Correct Answer
verified
A

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
Hypoxia-inducible factor 1 (HIF-1) is a ...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
E

Which statement is TRUE regarding the gamma ( $\gamma$ ) subunit of ATP synthase?

Correct Answer
verified

The ATP synthase F₁ portion contains many subunits arranged in a cyclic pattern, yet we cannot really describe it as having cyclic symmetry. Why?

Correct Answer
Answered by ExamLex AI
ATP synthase is a complex enzyme that pl...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
(1) NADH is transported into the mitocho...
View Answer

Correct Answer
Answered by ExamLex AI
The current model for how the proton mot...
View Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
1) Genetic evidence: Mitochondria have t...
View Answer