Oxidative Phosphorylation Flashcards
Stages of fuel oxidation
- Fuel
- release CO2 - Reduced coenzymes (NADH, FADH2)
- release H20 - ATP
Fuel oxidation provides energy for processes through generation of what?
Reduced coenzymes, NADH and FADH2
Anaerobic glycolysis (3)
- carbohydrates may be used to generate ATP through a non- oxidative pathway
- fast
- glucose –> lactate
Oxidative phosphorylation
-definiton
The process by which the oxidation of reduced nucleotide coenzymes is coupled to the synthesis of ATP
Oxidative phosphorylation is based on:
Chemiosmosis: energy for ATP synthesis is provided by an electrochemical gradient across the INNER MITOCHONDRIAL MEMBRANE
Electrochemical gradient is generated by components of the…
Electron transport chain, which pump protons across the inner mitochondrial membrane as they accept and donate electrons
In fuel metabolism
- what is oxidized
- what is reduced
- fuel donates electrons, it is oxidized
- NAD+ and FAD accept electrons, it is reduced
3 ways in which compounds can e oxidized in the body:
- the transfer of electrons from the compound as a hydrogen atom or a hydride ion
- the direct addition of oxygen from O2
- the direct donation of electrons (ex: Fe2+ –> Fe3+)
Reduction potential
- definition
- meaning of E’
- is a measure of the energy change when that compound accepts electrons, E’o (in volts)
- willingness of the compound to accept electrons
Reduction potential
-characteristics
-the more negative the reduction potential of a compound, the greater is the energy available for ATP generation
Oxidative phosphorylation
-generation of ATP requires: (5)
- an electron donor (NADH or FADH2)
- an electron acceptor (O2)
- ATP synthase
- an inner mitochondrial membrane impermeable to protons
- all components of the electron transport chain
Electron transport chain
-order of complexes (7)
- Complex I
- Complex 2
- Coenzyme Q
- Complex 3
- Cytochrome C
- Complex 4
- ATP synthase
Name of complex I, II, III, IV
I: NADH dehydrogenase
II: Succinate dehydrogenase
III: Cytochrome b-c 1 complex
IV: Cytochrome c oxidase
Complex I, III, IV
-definition
-multi- sub-unit protein complexes spanning the inner mitochondrial membrane
Name of the final electron acceptor in the electron transport chain
O2
NADH dehydrogenase (complex I) (3)
- in the inner mitochondrial membrane
- FMN accepts two electrons from NADH and is able to pass single electrons to the Fe-S centers
- Fe-S centers transfer electrons to CoQ
Succinate dehydrogenase (complex II) (5)
- part of the TCA cycle
- accepts electrons from FAD, which acquires them from fatty acid oxidation and other pathways
- passes electrons (2) to CoQ
- FAD is at the same energy level as CoQ, there is NO energy released as electrons are transferred
- does not span the membrane, DOES NOT have a proton pumping mechanism
Coenzyme Q
- quinone derivative
- hydrophobic tail
- transfers electrons to complex III
- mobile carriers
Coenzyme Q can accept hydrogen atoms from:
- FMNH2, produced on NADH dehydrogenase
- FADH2, produced on succinate dehydrogenase
Cytochromes
- characteristics
- chain which electrons are passed along the chain
-each contains a heme group
CoQ –> cytochrome b-c 1 (complex III) –> C (travels to) –> complex IV
Cytochrome oxidase (Complex IV)
- cytochrome a + a3
- it is the only electron carrier in which the here iron has an available coordination site that can react directly with O2
- at this site, the transported electrons and free protons are brought together –> O2 is reduce to water
Electrochemical gradient: the membrane potential and the proton gradient
- external face of the membrane
- inter membrane space
- the external face of the membrane is charged positive relative to the matrix side
- the inter membrane space has a higher proton concentration and there is more acidic than the matrix
ATP synthase
-structure (4)
- F0, inner membrane portion
- F1, matrix portion, headpiece
- F0 –> 12 subunits
- F1 –> 3 alpha and beta subunit pairs, Beta subunit contains a catalytic site for ATP synthesis
ATP synthase
-how it works (4 steps)
- proton re-enter the matrix by passing through the alpha subunit at F0
- the influx of protons through the proton channel turns the rotor
- F0 rotation causes conformational changes in the F1 domain that allow it to bind ADP+ Pi
- ADP is phophorylated to form ATP
How many protons are needed to complete ONE TURN of the rotor and synthesize 3 ATP?
12 protons
4H+ need to pass through the channel to make how many ATP?
1 ATP
How many H+ are pumped at complex:
- I
- III
- IV
I: 4H+
III: 4H+
IV: 2H+
How many H+ pass and how many ATP are formed when:
- NADH is oxidized
- FADH2 is oxidized
- 10H+, 2.5 ATP formed
- 6H+, 1.5 ATP formed
Uncoupling proteins (4)
- occur in the inner mitochondrial membrane
- create a “proton leak”, allow protons to re-enter the matrix without energy being captured as ATP
- energy is release as heat, non- shivering thermogenesis
- brown fat ex
Regulation of oxidative phosphorylation mainly depends on:
SASKIA AND MANU UNDERSTAND HISTOLOGY
- Supply of NADH, FADH, ADP and Pi
- ATP/ ADP ratio
- Magnitude of the membrane potential
- Uncoupling proteins
- Hormonal factors
Regulation at complex IV
- ADP
- Ca2+
- Phosphorylation/ dephosphorylation
Inhibitors of the electron transport chain (4)
- prevent the passage of electrons by binding to a component of the electron transport chain
- blocks the oxidation/ reduction reaction
- electrons are fully reduced before the block, electrons are oxidized after the block
- it inhibits also ATP synthesis because these processes are tightly coupled
At Complex I, III and IV electron transfer is accompanied by….
Proton pumping across the membrane
