Chapter 15 - Oxidative Phosphorylation

Front 1

What two chemical equations are associated with oxidative phosphorylation?

Back 1

A(oxidized) + B(reduced) <----> A(reduced) + B(oxidized)

FADH2(reduced) + Q(oxidized) <----> FAD(oxidized) + QH2(reduced)

Front 2

What states are the two reactants in in oxidation reduction?

Back 2

One reactant is in the oxidized state while the other is in its reduced state

Front 3

What is oxidation?

Back 3

Loss of electrons

Front 4

What is reduction?

Back 4

Gain of electrons

Front 5

What does reduction potential indicate?

Back 5

A substance's tendency to accept electrons

Front 6

What does the actual reduction potential depend on?

Back 6

The actual concentrations of oxidized and reduced species

Front 7

What is the Nerst Equation?

Back 7

E = E(degree)' - {[RT] / [nF]} ln { [A(reduced)] / [A(oxidized)] }

Front 8

What can the free energy change be calculated from?

Back 8

The change in reduction potential

Front 9

What is the equation to calculate deltaE(degree)'?

Back 9

deltaE(degree)' = [E(degree)'] (e-acceptor) - [E(degree)'] (e-donor)

delta

Front 10

What is the equation to calculate deltaG(degree)'?

Back 10

deltaG(degree)' = - nF [deltaE(degree)'] or

deltaG = - nF deltaE

Front 11

Describe the overview of the mitochondrial electron transport

Back 11

Passing electrons to a molecule "below" (i.e. more positive) on this scale as a deltaG > 0, or is favorable

NADH is the first electron transport donor on this scale, and O2 is the final electron acceptor, and it is reduced to H2O

Front 12

What happens to the redox potential energy of NADH and FADH2 in mitochondrial electron transport?

Back 12

It is released stepwise via the electron transports chain

Front 13

What is the electron transport chain associated with?

Back 13

The mitochondrial inner membrane

Front 14

What does the electron transport chain include?

Back 14

Integral and peripheral membrane proteins

Membrane localized low molecular weight compounds

Front 15

What do protein components use to carry electrons?

Back 15

Metal-containing prosthetic groups or flavins

Front 16

What binds to ubiquinone?

Back 16

Complex I

Front 17

What are the characteristics of the structure of a bacterial complex?

Back 17

FMN and Fe-S clusters are cofactors in space-filling representation

Q binding site

Part of the protein has membrane-spanning a helices

Front 18

What is Complex I of mitochondrial electron transport also known as?

Back 18

NADH: ubiquinone oxidoreductase

Front 19

What are the characteristics of Complex I of mitochondrial electron transport?

Back 19

A complex of proteins that includes a flavoprotein (contains FMN) and proteins with Fe-S centers

These proteins provide two centers for oxidation reduction reactions

FMN <----> FMNH2

Fe3+ <----> Fe2+

Front 20

What is Complex I of mitochondrial electron transport responsible for?

Back 20

Transfers electrons from NADH to Q

Front 21

How does Complex I transfer electrons from NADH to Q?

Back 21

Electron transfers from NADH and FMN, then from FMN to Fe-S, from Fe-S to Q

As electrons are transferred from NADH to ubiquinone, Complex I transfers four protons from the matrix to the intermembrane space

Front 22

How many electrons can FMN pick up from NADH?

Back 22

Two

Front 23

What do iron sulfur-clusters undergo?

Back 23

One-electron transfer reactions

Front 24

What is Complex II also referred to as?

Back 24

Succinate dehydrogenase, a component of the TCA cycle

Front 25

What is succinate dehydrogenase?

Back 25

A protein that includes a flavoprotein (contains FAD) and Fe-S

Front 26

What are the characteristics of Complex II?

Back 26

This protein provides two centers for oxidation reduction reactions

FAD <----> FADH2

Fe3+ <----> Fe2+

Front 27

What oxidation reactions contribute to the ubiquinol pool?

Back 27

Succinate dehydrogenase produced QH2 during the citric acid cycle

QH2 is also produced during fatty acid oxidation

Front 28

What is ubiquinone also referred to as?

Back 28

Coenzyme Q

Front 29

What are the characteristics of ubiquinone in mitochondrial electron transport?

Back 29

A membrane soluble low molecular weight compound

Shuttles electrons and protons from Complex I and Complex II to Complex III

Long hydrophobic tail keeps ubiquinone anchored to the mitochondrial inner membrane

Front 30

What is the function of Complex III in mitochondrial electron transport?

Back 30

Transfers electrons frrom ubiquinol to cytochrome c

Front 31

What are cytochromes?

Back 31

Proteins with heme prosthetic groups

Front 32

What are the characteristics of cytochrome c?

Back 32

Unlike he heme groups in hemoglobin, heme in cytochrome c undergoes reversible one-electron transfers

The central iron atom is either oxidized (Fe3+) or reduced (Fe2+)

Front 33

What is the function of peripheral membrane protein?

Back 33

Shuttles electrons and protons from Complex III to Complex IV

Front 34

What are the characteristics of Complex IV?

Back 34

A complex of proteins that contains two cytochrome and proteins with copper centers

These proteins provide multiple centers for oxidation reduction

Fe3+ <----> Fe2+

Cu2+ <----> Cu3+

Reduces oxygen to H2O

For every two electrons donated by cytochrome c, two proteins are translocated into the imtermembrane space

Two protons from the matrix are also consumed in the reaction:

1/2 O2 --> H2O

Front 35

Describe the Q cycle

Back 35

The circuitous route of electrons from ubiquinol to cytochrome c is describe be the Q cycle

Front 36

What is the first step of the Q cycle?

Back 36

In the first round, QH2 donates one electron to the iron-sulfur protein (ISP). The electron then travels to cytochrome c1 and then cytochrome c

Front 37

What is the second step of the Q cycle?

Back 37

QH2 donates its other electron to cytochrome b. The two protons from QH2 are released into the intermembrane space

Front 38

What is the third step of the Q cycle?

Back 38

The oxidized ubiquinone diffuses another quinone-binding site, where it accepts the electron from cytochrome n, becoming a half-reduced semiquinone (+Q-)

Front 39

What is the forth step of the Q cycle?

Back 39

In the second round, a second QH2 surrenders its two electrons to Complex III and its two protons to the intermembrane space. One electron goes to reduce cytochrome c

Front 40

What is the fifth step of the Q cycle?

Back 40

The other electron goes to cytochrome b and then to the waiting semiquinone produced in the first part of the cycle. This step regenerates QH2 using protons from the matrix

Front 41

What are the results of the Q cycle?

Back 41

Two electrons from QH2 reduce to two molecules of cytochrome c

Four protons are pumped into the intermembrane space

Two from QH2 in the first round

Two from QH2 in the second round

Front 42

Where does the electron transport take place?

Back 42

The mitochondrion, this is also where the citric acid cycle takes place

Front 43

What is the function of the malate-asparate shuttle?

Back 43

Transports reducing agents across the inner mitochondrial membrane

A different transport system is used to move ATP from the matrix to the cytosol

Front 44

What is the function of ATP translocase protein?

Back 44

Imports ADP and exports ATP

Front 45

What permits simultaneous movement of Pi and H+?

Back 45

A symport protein

Front 46

What occurs during oxidative phosphorylation?

Back 46

Complex I, Complex III, and Complex IV pump protons across the inner mitochondrial membrane

Front 47

What does the pumping during oxidative phosphorylation generate?

Back 47

Pumping uses the energy liberated from the oxidation of NADH and FADH2

Pumping generates a membrane potential because it generates an electrochemical gradient

Negative inside, positive outside

Alkaline inside, acidic outside

Front 48

What does the imbalance of protons in oxidative phosphorylation represent?

Back 48

A source of free energy also called a protonmotive force, that can drive the activity of an ATP synthase

Front 49

During oxidative phosphorylation, what happens as protons move back into the matrix through a special transmembrane protein?

Back 49

The energy stored in this electrochemical gradient is used to make ATP

Front 50

What is the protein that taps the electrochemical proton gradient to the phosphorylate ADP?

Back 50

ATP synthase, or Complex V

Front 51

What is the function of ATP synthase?

Back 51

Use the electrochemical gradient to drive phosphorylation

Front 52

What is the ATP synthase complex?

Back 52

Large transmembrane complex that faces into the mitochondrial matrix

F0: proton pore

F1: ATP synthesizing subunit

Front 53

What does the ATP synthase complex generate?

Back 53

1 ATP for every three protons that pass through it

From the oxidation of NADH

10 protons pumped, ~3 ATP synthesized

From the oxidation of FADH2

6 protons pumped, ~2 ATP synthesized

Front 54

Describe the P:O ratio of oxidative phosphorylation

Back 54

P:O ratio= # phosphorylations of ADP per # of oxygen atoms reduced

P:O rations will not be integral because chemical energy becomes a protonmotive force, the mechanical movement of ATP synthase and back to chemical energy

Front 55

Describe how the rate of oxidative phosphorylation depends on the rate of fuel catabolism

Back 55

Oxidative phosphorylation is regulated by the availability of reduced cofactors (NADH and QH2) produced by other metabolic proceses