BCH210H1 Lecture Notes - Lecture 29: Coenzyme Q10, Cytochrome C Oxidase, Reduction Potential

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amethystfly536

25 May 2018

School

UTSG

Department

Biochemical Engineering and Applied Chemistry

Course

BCH210H1

Professor

Stavroula Andreopoulos

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Lecture 29: Electron Transport

Mitochondrial Bioenergetics

• Mitochondrial inner membrane has the matrix

• Conversion of pyruvate to acetyl CoA → CREB cycle with

8 different enzymes that catalyzes decarboxylation

steps → regenerate oxaloacetate

• 7/8 are soluble, 1/8 (succinate dehydrogenase) membrane bound and

participates in electron transport chain

• Reduced electron carriers (NADH, FADH2 made that will donate electrons)

- Protons are passed across Complex I,II,III,IV

- Also pumping protons across mitochondrial inner membrane where

complex V will use the gradient to generate ATP

• There is a change in energy that drives the protons across the gradient

through the complexes so that the proton influx can flow down the gradient in

order to generate ATP

• NADH donates 2 electrons to complex I (NADH-Q oxidoreductase)

• 2 electrons passed on to coenzyme Q (electron carrier)

• They are passed onto complex III (Q-cytochrome c oxidoreductase), to

complex IV (cytochrome C oxidase)

• Final electron acceptor is O2

• Complex II (succinate-Q reductase) because we are accepting electrons from

succinate to FADH2 to Q (another path to pass electrons)

• Complex I pumps 4 protons across the membrane, 4 protons for complex III and 2 protons for complex IV

- Energy for change in conformation comes from change in reduction potential

Electron transfer potential

• Stadard Redutio Potetial E’o – a oleule’s tede to e oidized or reduced

- Change in redox potential from negative to more positive (more likely to give up

electrons → prefer to gain electrons = change in gibs free energy to pump protons)

- Positive SRP – more likely to accept electrons, negative SRP – more likely to give up electrons

- Inversely related (positive redox potential change, negative gibs free energy change = favorable process)

• ΔG°’ = -  F ΔE´o

- n = number of electrons

- How much energy is released as we pass electrons from one molecule to another

• F = 96,485 J/Vmol

Electron transfer potential calculation

• Normally reduction equation

• NADH has negative E´o, it prefers to go reverse direction (donate

electrons)

• Oxygen has positive E´o, it prefers to go forward (accept electron)

• What is the change in reduction potential? (acceptor molecule – donor

molecule) FLIP the (-/redox equation)

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Electro Trasport Chai

• Electron transfer potential of NADH or FADH2 is measured by standard reduction potential, E´o

• Electrons are passed from carrier to carrier

• Good reducing agents give up electrons easily and have negative E´o values

• Strong oxidizing agents have a greater affinity for electrons and have positive E´o values

• Passage of electrons down the chain (from – to +) results in a free energy change that establishes a proton

gradient that is used to make ATP

How are electrons transported

• Electrons are passed through a variety of prosthetic groups

- FMN (complex I) and FAD (complex II) groups

- Iron-sulfur complexes (complex I, II, III)

- Coenzyme Q (ubiquinone) (complex I, II to III)

- Cytochromes (complex III and IV)

- Protein-bound copper (complex IV)

• Changes in reduction potential drives pumping of protons

• The final electron acceptor is oxygen

Flavin mononucleotide (FMN)

• NADH + H+ + FMN → NAD+ + FMNH2

- NADH donating electron in the form of hydride

Iron-sulfur (FeS) clusters

• Fe can accept electrons and donate them

(cycle between ferrous and ferric state)

• Iron molecules coordinated to sulfur

groups in cysteine side chains

Single vs. double electron carriers

• 2 electrons (from NADH or FADH2) coming in but

some molecules can only accept 2 or 1 electron

depending on the carrier

- Need 2 FeS molecules because each Fe can only

carry one electron

Coenzyme Q/ubiquinone (CoQ, Q, UQ)

• Accepts electrons from I or II and

donates to III

• Fatty acid tail like – hydrophobic

- Anchors this molecule in the

membrane but mobile enough

to pick up electrons and pass

on electrons to complex III

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BCH210H1 Full Course Notes

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Document Summary

Mitochondrial bioenergetics: mitochondrial inner membrane has the matrix, conversion of pyruvate to acetyl coa creb cycle with. 8 different enzymes that catalyzes decarboxylation steps regenerate oxaloacetate: 7/8 are soluble, 1/8 (succinate dehydrogenase) membrane bound and participates in electron transport chain, reduced electron carriers (nadh, fadh2 made that will donate electrons) Energy for change in conformation comes from change in reduction potential. Electron transfer potential: sta(cid:374)dard redu(cid:272)tio(cid:374) pote(cid:374)tial (cid:894)e"o(cid:895) a (cid:373)ole(cid:272)ule"s te(cid:374)de(cid:374)(cid:272)(cid:455) to (cid:271)e o(cid:454)idized or reduced. Change in redox potential from negative to more positive (more likely to give up electrons prefer to gain electrons = change in gibs free energy to pump protons) Positive srp more likely to accept electrons, negative srp more likely to give up electrons. Inversely related (positive redox potential change, negative gibs free energy change = favorable process: g " = - (cid:374) f e o. How much energy is released as we pass electrons from one molecule to another: f = 96,485 j/vmol.

Related Questions

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.

apricotgoose897

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.

1. During the TCA cycle, four reactions occur in which a pair of electrons are transferred from a substrate to an electron accepting coenzyme. These reactions are catalyzed by?

2.During the TCA cycle, four reactions occur in which a pair of electrons are transferred from a substrate to an electron accepting coenzyme. These reactions are catalyzed by?

3.Potent respiratory poison, including carbon monoxide, azide and cyanide have their toxic effect by binding to the heme a3 site of _____.

4.The first step in the TCA cycle is the condensation of the two-carbon acetyl group with a four-carbon _____ to form a six-carbon citrate molecule?

5.The inner mitochondrial membrane is virtually devoid of ____, and and rich in ____, which are characteristics of bacterial plasma membranes.

6.Iron sulfur centers are joined to the protein by linkage to a sulfur atom of a/n ___.

7.Decarboxylation of pyruvate and transfer of the acetyl group to CoA , along with the reduction of NAD₊ is catalyzed by ___.

8.When FADH₂ is the electron donor, electrons are passed directly to ____ in the respiratory chain

9.With the exception of ____, all of the redox centers within the respiratory chain that accept and donate electrons are prosthetic groups.

10.It iis evident fromt eh net equation fo the TCA cycle that the primary products of the pathway are the reduced coenzymes _____.

11. Complex III catalyzes the transfer of electrons from ___ to ___.

12. The passage of a pair of electrons from NADH to ubiquinone in the respiratory chain is accompanied by movement of roughly four protons from (the) ___ to (the) ___.

13. When NADH is the electron donor, electrons pass the respiratory chain by means of ____.

14. The matrix of the mitochondrion has a gel-like consistency owing to the presence of a high conentration of _____.

These are questions I missed on a quiz the instructor does not post what the answers should be and has not responded to my emails please help.

Thanks,

Amber

BCH210H1 Lecture Notes - Lecture 29: Coenzyme Q10, Cytochrome C Oxidase, Reduction Potential

BCH210H1 Full Course Notes

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