BCH210H1 Lecture Notes - Lecture 27: Reduction Potential, Electron Transport Chain, Atp Synthase

19. Which of the following is a component of Succinate dehydrogenase in Electron transport chain?

A. Niacin

B. FMN

C. FAD

D. Coenzyme Q

E. Lipoic acid

20. In electron transport the flow of electrons:

A. is bidirectional

B. goes from a high energy state to a low energy state

C. takes place in the outer mitochondrial membrane

D. are used to pump H+ into the mitochondrial matrix

21. Which of the following statements about the electron transport chain is NOT correct

A. It is located in the inner mitochondrion membrane

B. Cytochrome c accepts electrons from complex II

C. Cytochrome c oxidase (complex IV) accepts electrons from Cytochrome c

D. Complex I is called NADH dehydrogenase

E. Coenzyme Q accepts electrons from complex I and complex II

22. In the electron transport chain, the enzyme cytochrome C oxidase:

A. Uses H2O as a substrate

B. Produces HOOH as a product

C. Cannot function if oxygen is absent

D. Accepts electrons from hydrogen ions

E. Uses ADP and Pi as substrates

Can you answer the following questions:

1. Carbon monoxide is considered toxic because it acts on Complex IV. How would the addition of carbon monoxide to actively respiring mitochondria affect the relative oxidation-reduction states of all components of the electron-transport chain?

A) All four complexes would remain oxidized because they function as a multisystem complex.

B) Complexes I and III would be reduced, but complexes II and IV would be oxidized because the

electrons come from FADH2 oxidation, not NADH.

C) Complexes I, II, and III would be oxidized but Complex IV would remain reduced.

D) Complexes I, II, and III would be reduced and Complex IV would be oxidized.

E) All four complexes would remain reduced because they function as a multisystem complex.

2. Electrons are not very soluble in hydrophobic environments such as a bilipid membrane. What evidence is there that electrons move from complex to complex through the lipid membrane?

A) Cytochrome C is the electron carrier in the membrane and undergoes a head-over-heel flip to set up the proton gradient.

B) Cytochrome C is the electron carrier in the membrane and contains a cydrophoric porphyrin center.

C) CoQ is the electron carrier within the membrane and seems to be confined to the respirasome.

D) CoQ is the electron carrier within the membrane and it contains a hydrophobic porphyrin center.

E) FeS clusters are the carriers within the membrane and the electrons move from one cluster to the

next in a chain-like fashion.

3. What is the rationale for saying that “electrons flow down the electron-transport chain”?

A) Electrons flow from oxidized carriers to reduced carriers in discrete steps like a staircase.

B) Electrons flow from half-reactions with more positive redox potentials to more negative.

C) Electrons flow from reactions that continuously generate negative free energy values.

D) Electrons flow from the outer surface to the inner surface, a top down perception.

E) Because we think of electrons flowing like a liquid, the only direction electrons can flow is down.

Which of the following is a substrate or component of complex IV:

a. FMN

b. CuB

c. oxidized cytochrome c

d. Fe-S protein.

F₀F₁ ATP synthase:

a. has a c-ring that can only be made of 8-subunits

b. requires 12 protons to make 3 ATP in all mammalian tissues.

c. converts an electrochemical gradient into mechanical energy to drive the removal of ATP from its active site.

d. None of the above.

Throughout the course we discussed the impact that the removal of oxygen would have on cellular metabolism during strenuous exercise and in this last unit applied it to mitochondrial metabolism. Given these discussions we can say that anaerobic conditions:

a. lead to the reduction of each complex in the electron transport chain

b. lead to the accumulation of NADH in the matrix of the mitochondria.

c. lead to a diminished activity of ATP synthase.

d. All of the above.

The addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria in which an inhibitor of ATP synthase is present along with the reduced electron carrier succinate will cause which of the following to occur?

a. Proton flow from the N to P-side via complex II.

b. The concentration of NADH to increase in the matrix due to subsequent inhibition of the electron transport chain.

c. Increased rate of oxygen reduction.

d. Decreased flux through complex III.