Oxidative Phosphorylation I Flashcards by Joel Glotfelty

ATP can be made during glycolysis, in an anaerobic process, but the most important source of ATP synthesis is

-An aerobic process

Oxidative phosphorylation

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Involves a series of oxidation/reduction reactions, beginning with the NADH and FADH2 produced in the citric acid (TCA) cycle and ending with the reduction of oxygen to water

Oxidative phosphorylation

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The oxygen required for this process is transported to every tissue in the body by

Hemoglobin

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The process of oxidative phosphorylation takes place in the

Mitochondria

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Oxidative phosphorylation is unique in that it has a key step which forms a

Proton gradient across the membrane

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Oxidative phosphorylation is also unique in using proteins made from which two genomes?

) Our nuclear genome

2. ) Small mitochondrial genome

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Cyanide results in death because it inhibits

Oxidative phosphorylation

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Accumulated defects in the process, through free radical damage or other causes, may be involved in aging and many common neurodegenerative diseases, such as

Alzheimers and Parkinson’s

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The use and transfer of energy in biological systems, and it must follow the same thermodynamic principles that hold for all reactions

Bioenergetics

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Some reactions give off energy, such as

Catabolic reactions

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Some reactions consume energy, such as

Anabolic reactions

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The free energy value when all of the reactants and products are present at 1M concentration, neutral pH, standard conditions

Standard Free Energy (Delta-Go)

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Reaction goes spontaneously as written and will give off energy if

Delta G is negative

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Reaction will not go spontaneously as written and energy must be added to the system if

Delta G is positive

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The reaction is at equilibrium if

Delta G is zero

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The delta-G values of subsequent reactions are

-reactions can be couple for spontaniety

Additive

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Made using energy from catabolic reactions and is then used ot drive anabolic reactions

ATP

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A relatively simple molecule: it has an adenine (nitrogenous base), attached to a ribose (5 carbon sugar), which is bound to a chain of three phosphate groups

ATP

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How many high-energy phosphate bonds does ATP have?

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Removal of the terminal phosphate gives ADP and gives off

delta-D = -7.3 kcal/mol

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The high charge of the three phosphates in ATP produces electrostatic repulsion which is relieved when it is hydrolyzed to form

ADP

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The existence of four possible resonance forms for the inorganic phosphate Pi products leads to

Resonance stabilization

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ATP works by direct transfer of a phosphate group to

Another molecule

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Acts as an essential link between energy producing and energy consuming processes

ATP

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The energy from oxidation of compounds is conserved in

ATP

What is the average consumption of ATP per 24 hours in the average human?

40 kg

During strenuous exercise, the rate of ATP utilization can be as high as

0.5 kg/min

A typical lipid bilayer, which is permeable to small molecules, but not permeable to proteins and other large molecules

Outer mitochondrial membrane

The narrow space between the outer and inner membranes

Intermembrane space

Located in the intermembrane space

Apoptotic molecules

Has many infoldings known as cristae, which increases its surface area

Inner mitochondrial membrane

This inner membrane is a most unusual membrane, in having extremely high protein content and in being impermeable to

Small and large molecules

Even K+ ions, Ca++ ions, ATP, ADP, protons and OH- groups cannot diffuse through the

Inner mitochondrial membrane

This membrane is the site of the electron transport chain and the process of oxidative phosphorylation

Inner mitochondrial membrane

The ATP synthase molecules which directly synthesis the ATP from ADP and phosphate are embedded in

Inner mitochondrial membrane

The mitochondrial matrix is the site of the

TCA cycle and FA oxidation

There are also small circular mitochondrial DNA molecules (mtDNA) in the

Matrix

These mtDNA molecules code for 13 polypeptide chains, all of which involves in

Oxidative phosphorylation

This mtDNA also codes for

tRNA and rRNA molecules

The mitochondrial genome codes for just

13 proteins

In the inner mitochondrial membrane, the electron transport chain undergoes a series of successive

Oxidation and reduction reactions

These redox reactions generate energy used to form a proton gradient across the

Inner mitochondrial membrane

This proton gradient is dissipated through the ATP synthase and leads to the formation of

ATP

There are 5 large protein complexes in the inner mitochondrial membrane, called complexes

I-V

Complexes I, II. III. and IV are all part of the

Electron transport chain

These 4 complexes work together with 1. ) The lipid soluble? 2. ) The water soluble?

1. ) Coenzyme Q | 2. ) Cytochrome C

The electron transport chain is also known as the respiratory chain, because of its need for oxygen as the terminal acceptor of

Electrons

The ATP synthase (also known as ATPase) which uses the energy of the proton gradient to catalyze the formation of ATP

Complex V

What is an oxidation-reduction reaction?

OIL-RIG

The loss or gain of an electron may be accompanied by a

Proton

What are three forms of reduction?

1. ) Reduction by gain of electron 2. ) Reduction by gain of hydrogen atom 3. ) Reduction by gain of hydride ion

The standard oxidation reduction potential Eo’ (Volts) is measure of the affinity for a compound to

Accept or Donate electrons

The more POSITIVE the standard potential, the higher the affinity for

Electrons (Reduction)

Tend to lose electrons and reduce other compounds (as they get oxidized)

Strong reducing agents

Such strong reducing agents have a

Low or negative Eo

Want to accept electrons and oxidize other compounds (as they get reduced); they have a high positive Eo

Strong oxidizing agents

What are two examples of strong reducing agents?

NADH and FADH2

What is an example of a strong oxidizing agent?

Oxidation-reduction reactions give off energy, and the amount of energy released depends on the standard oxidation potentials of the

Oxidizing and reducing pairs

It is known that the transfer of 2 electrons from NADH through all the components of the electron transport chain leads to the formation of

3 ATP molecules

The standard free energy change for the formation of ATP from ADP and Pi is DGo =

7.3 kcal/mol

Electrons are transferred from the products of the TCA cycle, NADH and succinate, to O2 through

Complexes I - IV, Coenzyme Q,a nd cytochrome C

Complex I is an

NADH-CoQ oxidoreductase

Accepts electrons directly from NADH in the mitochondrial matrix

Complex I

Cannot accept electrons from NADH when it is on the intermembrane space side of the inner mitochondrial membrane

Complex I

NADH gets oxidized to NAD+ and is available for anotherround of the TCA cycle, while complex I gets

Reduced

The largest complex in the electron transport chain. It consists of at least 46 polypeptide chains, plus a tightly bound flavin mononucleotide (FMN) and many iron sulfur centers

Complex I

Complex II is

Succinate Dehydrogenase

Succinate dehydrogenase is reduced by -from the TCA cycle

FADH2

Embedded in the inner mitochondrial membrane, and is reduced by FADH2

Succinate dehydrogenase

Succinate dehydrogenase then reduces -makes a branch at the CoQ point in the chain

CoQ

The electrons from FADH2 that to CoQ can also come from glycerol-3-phosphate dehydrogenase as a part of the

G-3-P and fatty acyl CoA dehydrogenase

The acyl CoA dehydrogenase resides in the

Matrix

Accepts 2 electrons from a reduced iron sulfur group of complex I (together with 2 protons) leading to the reduced form

Coenzyme Q (CoQ, ubiquinone)

A small lipid soluble molecule in the membrane; it is the only component that is not a protein, and it can freely diffuse in the inner mitochondrial membrane

CoQ

The reduced form of CoQ, CoQH2 transfers its electrons to -In complex III

Cytochrome B

Complex III is reduced by CoQH2 and then passes its electrons to

Cytochrome C

Complex III consists of 11 subunits, including

1. ) Cytochrome B 2. ) Cytochrome C 3. ) Fe-S center

Electrons are transferred from CoQ to cyt b to cyt c1, and eventually to the next component

Cytochrome C

Cyt c gets reduced by complex III and it reduces

Complex IV

A single polypeptide chain with a single heme group

Cytochrome C

The only water soluble component of the electron transport chain. It is present in the intermembrane space of the mitochondrial and has a high positive charge on its surface

Cytochrome C

Binds to complex III electrostatically, from the intermembrane space side of the inner mitochondrial membrane and becomes reduced

Cytochrome C

Cyt c is also a trigger for

Apoptosis

The final component of the ETC

Complex IV (cytochrome oxidase)

Complex IV accepts electrons from Cyt c, and then coordinates the transfer of 4 electrons to

Oxygen (reducing it to water)

Consists of 11 polypeptide chains, including cyt a (which contains heme a) and cyt a3 (which contains heme a3), and two copper ions

Complex IV

The heme group of cyt a3 in its reduced state binds

The other cytochromes all have 6 ligands bound to the iron in the heme group and cannot react with

Oxygen

The transfer of 2 electrons from NADH through all the components of the electron transport chain to O2 generates a larger amount of energy (~53kcal/mol) and leads to the formation of

3 ATP molecules

The oxidation of 1 NADH leads to 3 ATP, while oxidation of succinate leads to

2 ATP

Oxidation reduction reactions in the electron transport chain lead to pumping of protons from the matrix to the

Outer side of the inner membrane

There are more protons on the outer side and fewer protons on the matrix side of the inner mitochondrial membrane. This gradient of protons (H+) generates both a

pH gradient and an electrical gradient

Thus the proton gradient generates an electrochemical or chemiosmotic gradient, which provides energy or a force, sometimes called the

Proton motive force

It is this proton-motive force or chemiosmotic gradient which provides the energy to synthesize

ATP

As the components of the electron transport chain are reduced and oxidized, there are 3 sites in electron transport at which a large amount of energy is given off. What are they?

1. ) NADH-CoQ reductase (I) 2. ) Cytochrome C reductase (III) 3. ) Cytochrome C oxidase (IV)

The actual synthesis of ATP takes place in a complex known as

ATP Synthase

Which portion of the ATP synthase is an integral part of the inner mitochondrial membrane?

Consists of a stalk and globular portion that extend from the inner mitochondrial membrane into the matrix

F1 portion of ATP synthase

The proton gradient that is generated across the inner mitochondrial membrane by the electron transport chain is used to rotate subunits of