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#21 Mitochondria & Oxidative Phosphorylation
Terms in this set (53)
Name three enzymes that donate electrons to the electron transport chain from their flavin (FAD) prosthetic group.
Succinate dehydrogenase, acyl-CoA dehydrogenase and glycerol phosphate dehydrogenase.
How many moles of ATP can be produced per mole of NADH?
How many moles of ATP can be produced per mole of FADH2?
In which organelle does oxidative phosphorylation occur?
Name the four complexes of the electron transport chain.
NADH:CoQ reductase (Complex I), Succinate:CoQ reductase (Complex II), Reduced:cyt c reductase (Complex III), and Cytochrome oxidase (Complex IV).
Which enzyme couples the dissipation of a proton concentration gradient to the production of ATP in mitochondria?
ATP synthase (also called F0F1 ATPase, H-dependent ATPase, or simply ATPase).
Which molecule catalyzes the transfer of electrons from Complex I and Complex II to Complex III?
Coenzyme Q (also called ubiquinone).
Which molecule catalyzes the transfer of electrons from Complex III to Complex IV?
What is the final electron acceptor in the electron transport chain?
A molecule of oxygen.
In which cellular compartment is the electron transport chain located?
The inner mitochondrial membrane.
How does the lipid:protein ratio of the outer mitochondrial membrane differ from that of the inner mitochondrial membrane?
The outer mitochondrial membrane is approximately half lipid and half protein, whereas the inner mitochondrial membrane is approximately 80% protein and 20% lipid.
What is the function of the protein porin with respect to mitochondria?
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.
Which phospholipid found only in the mitochondrial inner membrane enhances the membrane's lack of permeability to protons?
Cardiolipin (diphosphotidyl glycerol).
T/F. The outer mitochondrial membrane provides a barrier to proton diffusion.
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.
What are three ways in which mitochondrial DNA differs from nuclear DNA?
Mitochondrial DNA is circular, inherited maternally with no paternal contribution, and contains very few introns.
What is encoded by the genes in mitochondrial DNA?
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.
Where are all the enzymes of the TCA cycle and fatty acid oxidation synthesized?
They are synthesized as precursors in the cytoplasm. The precursors are then transported into the mitochondrion, where they are converted to mature proteins.
What is a 'matrix targeting sequence?'
It is a sequence of amino acids on the N-terminal of some precursor proteins. It directs these proteins to the mitochondria.
T/F. Mitochondrial protein import is an energy-dependent process and requires protein unfolding and refolding.
Which complexes of the electron transport chain directly accept electrons from NADH?
Complex I only.
Which complexes of the electron transport chain contain the cofactor flavin mononucleotide (FMN)?
Complex I only.
Which complexes of the electron transport chain contain the cofactor flavin adenine dinucleotide (FAD)?
Complex II only.
Which complexes of the electron transport chain contain iron-sulfur prosthetic groups?
Complex I, II and III.
Which complexes of the electron transport chain contain the transition metal copper?
Complex IV only.
What is the role of coenzyme Q (ubiquinone) in the electron transport chain?
It transfers electrons from both Complex I and Complex II to Complex III.
What is the role of mitochondrial cytochromes in the electron transport chain?
They transfer electrons sequentially from coenzyme Q to an oxygen molecule.
Which prosthetic group is common to all mitochondrial cytochromes?
The reduction potential of cytochromes in the electron transport chain ___________ (increases/decreases/does not change) from cytochrome b to cytochrome a3.
Which cytochrome in the electron transport chain accepts electrons from coenzyme Q?
Which cytochromes are a component of Complex III?
Cytochrome b and cytochrome c1.
Which cytochromes are a component of Complex IV?
Cytochrome a and cytochrome a3.
What is the location of cytochrome c in the mitochondria?
Cytochrome c is found on the outer side of the inner mitochondrial membrane.
How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex I?
How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex II?
None. Complex II does not pump any protons into the intermembrane space.
How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex III?
How many protons are pumped across the inner mitochondrial membrane during the transfer of two electrons through Complex IV?
What two additive terms make up the proton-motive force created by the electron transport chain?
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).
Which respiratory chain complex does not participate in the generation of an electrochemical proton transmembrane potential?
Name an inhibitor that binds to Complex I and prevents the reduction of coenzyme Q.
How does antimycin affect the oxidative production of ATP?
By binding to Complex III, preventing the transfer of electrons to Complex IV.
Cyanide and azide inhibit cellular respiration by binding to which component of Complex IV?
Both bind to the ferric (Fe3+) form of cytochrome a3.
Carbon monoxide inhibits cellular respiration by binding to which component of Complex IV?
It binds to the ferrous (Fe2+) form of cytochrome a3.
In the glycerol phosphate shuttle, cytoplasmic NADH is used to reduce _______ to _______.
Dihydroxyacetone-phosphate to glycerol-3-phosphate.
Which enzyme in the glycerol phosphate shuttle transfers electrons from glycerol-3-phosphate to coenzyme Q of the electron transport chain?
FAD-linked glycerol phosphate dehydrogenase.
Which component of ATP synthase contains the catalytic site for ATP synthesis and protrudes from the inner mitochondrial membrane into the matrix?
The F1 component.
Which component of ATP synthase forms a transmembrane channel that allows protons to flow across the inner mitochondrial membrane?
The F0 component.
What is the major limiting factor controlling the rate of both respiration and oxidative phosphorylation under normal physiologic conditions?
The availability of ADP.
What effect do uncouplers have on the rate of respiration and oxidative phosphorylation?
Uncouplers cause respiration to proceed at maximal rate, but without the production of ATP.
What mitochondrial enzyme is inhibited by oligomycin?
What is thermogenin?
It is an uncoupling protein found in the mitochondria of brown adipose tissue. It is involved in the generation of heat (non-shivering thermogenesis).
Which two transporters permit the transport of ATP, ADP and phosphate across the inner mitochondrial membrane?
The Pi/OH exchanger and the ATP/ADP exchanger.
Name two respiratory toxins that inhibit the inner mitochondrial membrane ATP/ADP exchanger.
Atractyloside and bongkrekic acid.
How many moles of ATP are produced from the complete oxidation of glucose via glycolysis, the TCA cycle and respiration?
36-38 moles of ATP per mole of glucose.
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