Oxidative Phosphorylation

what is the location of the electron transport chain (ETC)

inner mitochondrial membrane

what are the 3 stages of cellular respiration

1. Acetyl-CoA production

2. Acetyl-CoA oxidation

3. Electron transfer and oxidative phosphorylation

What is the importance/purpose of ETC

Generate proton gradient which powers ATP synthase

What are the components of the ETC

4 protein complexes (I,II,III,IV)

2 mobile electron carries; coenzyme Q/ubiquinone and cytochrome c

final electron acceptor and molecular oxygen

What is the location of ATP synthase

inner mitochondrial membrane

What is the connection of mitochondrial content to cellular function

mitochondria produce ATP (energy) that fuels cellular activities/processes, and involved in cell death/metabolism/signaling

How does mitochondria amount/concentration relate to cellular function

More ATP/energy needed within a cell = abundance of mitochondria (dark staining)

high energy demand = high mitochondria content

How does cytosolic NADH donate electrons to ETC

Dihydroxyacetone (DHAP) accepts NADH 2 e-, generating glycerol 3-phosphate, which is then reoxidized to DHAP in inner mitochondrial membrane. FAD reduced to FADH2, and the electrons are donated directly to Coenzyme Q

what does Glycerol 3-phosphate shuttle do

allows NADH to enter inner mitochondrial membrane and convert NADH to FADH2

What is the function of Electron transferring flavoprotein (ETF) in ETC transferring of electrons in regards to fatty acid oxidation

supply electrons from all available sources to CoQ via Q oxidoreductase transfer electrons from fatty acid oxidation

Why does electron transfer occur

difference in chemical potential for electrons between two species, driven by a reducing agent (molecules tendency to lose electrons) and oxidizing agent (molecules tendency to gain electrons)

How is the mitochondrial electrochemical gradient generated

generated by ETC

protons pumped across inner mitochondrial membrane as electrons lose energy

Electrical gradient generated; positive charge outside

Chemical gradient generated: outside membrane has lower pH than matrix

during electron transfer, how many protons are pumped for every oxidized FADH2 

6 H+

During electron transfer, how many protons are pumped across the membrane for every oxidized NADH

10 H+

what is the mechanism of action of inhibitors for Complex I

Blocking transfer of electrons from Fe-S centers to CoQ

what is Complex II inhibitors mechanism

block transfer of electrons from succinate dehydrogenase enzyme to CoQ

What is inhibitor mechanism for Complex III

block electron transfer from Cytochrome B to cytochrome C1

What is Complex IV inhibitor mechanism

bind to Complex IV and block electron transfer causing the final step in ETC to stop (electrons are NOT passed to oxygen)

What is the effect of mutations within Complex I subunit

resulting in incorrect assembly of subunit resulting in electron transport inefficiency

what complexes are Copper prosthetic group located, and how electrons are transported

Complex IV

Cu+ accepts 4 electrons to reduce O2 to H2O

What complexes are Cytochromes prosthetic groups located, and how are electrons transported

Complexes III, and IV, and mobile cytochrome C

electron transfer ring proteins that contain heme

what complexes are Flavin mononucleotide (FMN) prosthetic  groups located, and how are electrons transported

Complex I, and initial binding site for electrons from NADH

FMN → FMNH2 transfer electrons to Fe-S clusters

What complexes is Fe-S proteins prosthetic groups located, and how are electrons transported

Complexes I, II, & III

transfer electrons to and from CoQ

What are the 4 important prosthetic groups

Fe-S (iron-sulfur)

Cytochromes

Flavin mononucleotide (FMN)

Copper (Cu+)

What are the 2 important coenzymes involved in oxidative phosphorylation

Coenzyme Q (ubiquinone)

Cytochrome C

how are electrons transported between the 2 complexes, Coenzyme Q and Cytochrome C

while transporting electrons CoQ diffuse freely through inner mitochondrial membrane → oxidize CoQ (quinone) accepts electron forming ‘QH (semiquinone radical) → second electron accepted forming reduce form ubiquinol (QH2) → QH2 transfers electrons directly to cytochrome C

How are electrons transferred through Complex I

Complex I embedded in IMM

Hydride from NADH is transferred to FMN binding protein, electrons passed through several Fe-S clusters, then 2 electrons transferred to bound form of CoQ = QH2

how many protons are translocated from the matrix across IMM in Complex I, per NADH

4 H+

what is the process of electron transfer through Complex II/Succinate dehydrogenase (in TCA cycle)

Succinate oxidation generates FADH2, which then move through several Fe-S centers to CoQ

how many protons are pumped within Complex II and what are the consequences of it

None, change in free energy is insufficient to pump proteins

consequence: less ATP generated when FADH2 is electron donor

how are electrons transferred in Complex III

CoQ transfer electrons to cytochrome c reductase, 1 CoQ electron transferred to Fe-S protein, Cyt c1 and then to mobile electron carrier cytochrome c… 2nd electron is passed to CoQ and recycled in QH2 pool

how many electrons can cytochrome c carry

1

how many protons are pumped across inner mitochondrial membrane in Complex III

4H+

How are electrons transferred in Complex IV(cytochrome c oxidase)

Accepts electron from Cyt c

2 Cyt c electrons reduce half O2 → H2O

4 Cyt c electrons fully reduce O2 → H2O

Copper accepts electrons from Cyt c, transferring it to cytochromes a/a3, another copper, and finally to molecular oxygen

how many protons are pumped in Complex IV

2H+ pumped across IMM from matrix for every 2 electrons entering Complex IV from Cyt c