BIOCHEM 2EE3 Lecture Notes - Lecture 13: Conformational Change, Phosphorylation, Phosphate

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17 Sep 2016

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Recall that a lot of energy was packed away in electrons passed on to nadh and fadh2: these electrons are now used for reusable energy. In general, protein complexes are used to accept electrons and shuttle them, and to pump proteins out of the mitochondrial matrix into the intermembrane space: ex. Serve to shuttle the electrons b/w protein complexes. Carries are used since electrons do not diffuse very well on their own (it is charged and cannot pass through a hydrophobic membrane) Coenzyme q and cytochrome c are lipid soluble transporters. Within each protein complex there are several redox centres: can be reversibly reduced and re-oxidized (similar to nadh and fadh2) Redox centres are categorized as: coenzymes, fe-s clusters, cytochromes, cu. Each protein complex contains a combination of two or more of these types of redox centres. Nadh donates its electrons to complex i, complex i passes the electrons to complex iii, then to complex iv.

Related Questions

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 âelectrons flow down the electron-transport chainâ?

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.

Why does an electron have lower potential energy in an H-O bondthan in an O=O bond?

H has a higher electronegativity than O.

O=O is not stable.

O=O contains a double bond.

The electrons are closer to the oxygen atom in the H-O bond.

None of the answers are correct.

How is the energy from the electron transport chain used mostdirectly?

to form the bonds of a water molecule

to pump hydrogen ions across the mitochondrial inner membraneinto the mitochondrial intermembrane space

to join ADP with a phosphate

to decompose glucose into pyruvate

to rotate ATP synthase

Which process provides the energy needed to pump protons acrossthe mitochondrial membrane during oxidative phosphorylation?

the transfer of electrons in redox reactions

the breakdown of ATP to ADP

the rotation of the ATP synthase rotor

oxidation of isocitrate

None of the answers are correct.

What causes the ATP synthase rotor to spin?

the passing of electrons through ATP synthase

the movement of protons across the mitochondrial membrane

the movement of electrons across the mitochondrial membrane

the synthesis of ATP from ADP and a phosphate group

None of the answers are correct.

What of the following generates the proton-motive force duringoxidative phosphorylation?

buildup of NADH molecules at protein complex I

movement of H⁺ ions across the mitochondrial membraneduring electron transport

rotation of the ATP synthase rotor

joining of H⁺ ions with oxygen to form water

None of the answers are correct.

Suppose a microorganism invades a cell, causing damage to ATPsynthase. How would cellular respiration be affected?

Electrons could not be passed down the electron transportchain.

ADP could not be joined with a phosphate to form ATP.

Hydrogen ions could not be pumped into the mitochondrialintermembrane space.

The cell could not release any energy from the glucosemolecule.

Glucose could not be broken down into pyruvate.

Which molecules transport electrons from the citric acid cycleto the electron transport chain?

NADH and FADH₂

ATP and ADP

GTP and GDP

oxaloacetate and citric acid

None of the answers are correct.

Which type of reactions control the energy release from glucoseduring the citric acid cycle?

acid-base reactions

redox reactions

random reactions

All answers are correct.

None of the answers are correct.

What is the role of NAD⁺ in cellular respiration?

to receive electrons from the citric acid cycle and deliver themto the electron transport chain

to catalyze the synthesis of ATP from ADP

to accumulate in the mitochondrial intermembrane space tofacilitate ATP synthesis

to serve as a substrate to bind to acetyl-CoA at the beginningof the citric acid cycle

None of the answers are correct.

10.

Which molecule enters the citric acid cycle?

glucose

pyruvate

ATP

acetyl-CoA

None of the answers are correct.

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BIOCHEM 2EE3 Lecture Notes - Lecture 13: Conformational Change, Phosphorylation, Phosphate

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