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Biochemistry Exam 2 > L21- Mitochondria > Flashcards

L21- Mitochondria Flashcards

1
Q

Name three enzymes that donate electrons to the electron transport chain from their flavin (FAD) prosthetic group.

A

Succinate dehydrogenase, acyl-CoA dehydrogenase and glycerol phosphate dehydrogenase.

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2
Q

How many moles of ATP can be produced per mole of NADH?

A

3

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3
Q

How many moles of ATP can be produced per mole of FADH2?

A

2

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4
Q

In which organelle does oxidative phosphorylation occur?

A

Mitochondria.

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5
Q

Name the four complexes of the electron transport chain.

A

NADH:CoQ reductase (Complex I), Succinate:CoQ reductase (Complex II), Reduced:cyt c reductase (Complex III), and Cytochrome oxidase (Complex IV).

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6
Q

Which enzyme couples the dissipation of a proton concentration gradient to the production of ATP in mitochondria?

A

ATP synthase (also called F0F1 ATPase, H-dependent ATPase, or simply ATPase).

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7
Q

Which molecule catalyzes the transfer of electrons from Complex I and Complex II to Complex III?

A

Coenzyme Q (also called ubiquinone).

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8
Q

Which molecule catalyzes the transfer of electrons from Complex III to Complex IV?

A

Cytochrome c.

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9
Q

What is the final electron acceptor in the electron transport chain?

A

A molecule of oxygen.

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10
Q

In which cellular compartment is the electron transport chain located?

A

The inner mitochondrial membrane.

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11
Q

How does the lipid:protein ratio of the outer mitochondrial membrane differ from that of the inner mitochondrial membrane?

A

The outer mitochondrial membrane is approximately half lipid and half protein, whereas the inner mitochondrial membrane is approximately 80% protein and 20% lipid.

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12
Q

What is the function of the protein porin with respect to mitochondria?

A

Porin is a transmembrane protein found in the outer mitochondrial membrane. It renders the membrane permeable to most small metabolites that are of molecular weight <10,000 Da.

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13
Q

Which phospholipid found only in the mitochondrial inner membrane enhances the membrane’s lack of permeability to protons?

A

Cardiolipin (diphosphotidyl glycerol).

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14
Q

True or False. The outer mitochondrial membrane provides a barrier to proton diffusion.

A

False. The outer mitochondrial membrane is permeable to protons. In fact, the cytosol and the intermembrane space have approximately the same concentration of water soluble metabolites and ions.

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15
Q

What are three ways in which mitochondrial DNA differs from nuclear DNA?

A

Mitochondrial DNA is circular, inherited maternally with no paternal contribution, and contains very few introns.

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16
Q

What is encoded by the genes in mitochondrial DNA?

A

Two structural rRNA’s, 22 tRNA’s needed for mitochondrial protein synthesis, and 13 of the approximately 70 proteins that form the electron transport chain.

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17
Q

Where are all the enzymes of the TCA cycle and fatty acid oxidation synthesized?

A

They are synthesized as precursors in the cytoplasm. The precursors are then transported into the mitochondrion, where they are converted to mature proteins.

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18
Q

What is a ‘matrix targeting sequence?’

A

It is a sequence of amino acids on the N-terminal of some precursor proteins. It directs these proteins to the mitochondria.

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19
Q

True or False. Mitochondrial protein import is an energy-dependent process and requires protein unfolding and refolding.

A

True.

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20
Q

Which complexes of the electron transport chain directly accept electrons from NADH?

A

Complex I only.

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21
Q

Which complexes of the electron transport chain contain the cofactor flavin mononucleotide (FMN)?

A

Complex I only.

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22
Q

Which complexes of the electron transport chain contain the cofactor flavin adenine dinucleotide (FAD)?

A

Complex II only.

23
Q

Which complexes of the electron transport chain contain iron-sulfur prosthetic groups?

A

Complex I, II and III.

24
Q

Which complexes of the electron transport chain contain the transition metal copper?

A

Complex IV only.

25
Q

What is the role of coenzyme Q (ubiquinone) in the electron transport chain?

A

It transfers electrons from both Complex I and Complex II to Complex III.

26
Q

What is the role of mitochondrial cytochromes in the electron transport chain?

A

They transfer electrons sequentially from coenzyme Q to an oxygen molecule.

27
Q

Which prosthetic group is common to all mitochondrial cytochromes?

A

Heme.

28
Q

The reduction potential of cytochromes in the electron transport chain ___________ (increases/decreases/does not change) from cytochrome b to cytochrome a3.

A

Increases.

29
Q

Which cytochrome in the electron transport chain accepts electrons from coenzyme Q?

A

Cytochrome b.

30
Q

Which cytochromes are a component of Complex III?

A

Cytochrome b and cytochrome c1.

31
Q

Which cytochromes are a component of Complex IV?

A

Cytochrome a and cytochrome a3.

32
Q

What is the location of cytochrome c in the mitochondria?

A

Cytochrome c is found on the outer side of the inner mitochondrial membrane.

33
Q

How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex I?

A

4

34
Q

How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex II?

A

None. Complex II does not pump any protons into the intermembrane space.

35
Q

How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex III?

A

4

36
Q

How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex IV?

A

2

37
Q

What two additive terms make up the proton-motive force created by the electron transport chain?

A

A pH gradient (the mitochondrial matrix being more alkaline than the cytosol) and a membrane potential (the mitochondrial matrix being negatively charged relative to the cytosol).

38
Q

Which respiratory chain complex does not participate in the generation of an electrochemical proton transmembrane potential?

A

Complex II.

39
Q

Name an inhibitor that binds to Complex I and prevents the reduction of coenzyme Q.

A

Rotenone.

40
Q

How does antimycin affect the oxidative production of ATP?

A

By binding to Complex III, preventing the transfer of electrons to Complex IV.

41
Q

Cyanide and azide inhibit cellular respiration by binding to which component of Complex IV?

A

Both bind to the ferric (Fe3+) form of cytochrome a3.

42
Q

Carbon monoxide inhibits cellular respiration by binding to which component of Complex IV?

A

It binds to the ferrous (Fe2+) form of cytochrome a3.

43
Q

In the glycerol phosphate shuttle, cytoplasmic NADH is used to reduce _______ to _______.

A

Dihydroxyacetone-phosphate to glycerol-3-phosphate.

44
Q

Which enzyme in the glycerol phosphate shuttle transfers electrons from glycerol-3-phosphate to coenzyme Q of the electron transport chain?

A

FAD-linked glycerol phosphate dehydrogenase.

45
Q

Which component of ATP synthase contains the catalytic site for ATP synthesis and protrudes from the inner mitochondrial membrane into the matrix?

A

The F1 component.

46
Q

Which component of ATP synthase forms a transmembrane channel that allows protons to flow across the inner mitochondrial membrane?

A

The F0 component.

47
Q

What is the major limiting factor controlling the rate of both respiration and oxidative phosphorylation under normal physiologic conditions?

A

The availability of ADP.

48
Q

What effect do uncouplers have on the rate of respiration and oxidative phosphorylation?

A

Uncouplers cause respiration to proceed at maximal rate, but without the production of ATP.

49
Q

What mitochondrial enzyme is inhibited by oligomycin?

A

ATP synthase.

50
Q

What is thermogenin?

A

It is an uncoupling protein found in the mitochondria of brown adipose tissue. It is involved in the generation of heat (non-shivering thermogenesis).

51
Q

Which two transporters permit the transport of ATP, ADP and phosphate across the inner mitochondrial membrane?

A

The Pi/OH exchanger and the ATP/ADP exchanger.

52
Q

Name two respiratory toxins that inhibit the inner mitochondrial membrane ATP/ADP exchanger.

A

Atractyloside and bongkrekic acid.

53
Q

How many moles of ATP are produced from the complete oxidation of glucose via glycolysis, the TCA cycle and respiration?

A

36-38 moles of ATP per mole of glucose.

Biochemistry Exam 2 (12 decks)

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