Oxidative Phosphorylation Flashcards
what’s oxidative phosphorylation?
the coupling of electron transport with ATP synthesis
O2 + NADH + FADH2 + ADP + Pi + H+ –> ATP + FAD + NAD+ + H2O
where does TCA cycle occur?
in the matrix of mitochondria
fatty acid oxidation also occurs here
where does the ETC occur?
the individual components of ETC except cytochrome C are all located in the inner mitochondrial membrane
IMPORTANT: the inner membrane of mitochondria is a specialized structure that’s impermeable to most ions and molecules and the cristae of the inner membrane increase its surface area
also, the outer membrane is highly permeable
what does the entire ETC consist of?
- 4 large protein complexes (very complex, lots of subunits)
- 2 small independent components: ubiquinone and cytochrome C
what happens to the electrons of FADH2 that were collected during TCA?
FADH2 doesn’t transfer its electrons to complex I
succinate dehydrogenase (the same enzyme used to make FADH2 during TCA) is part of complex II so FADH2 transfers electrons directly to complex II
what happens in each step of the ETC?
a redox reaction where electrons are transferred from components with more negative reduction potentials to components with more positive reduction potentials
e- are conducted through the system from reduced coenzymes like NADH or FADH2 to oxygen
after every step, the electrons are at a lower energy state
the free energy released during this process drives the transport of protons from the matrix to the inter membrane space via three proton pumps
what are the three proton pumps?
complex I, III and IV
what is the flow of electrons through ETC?
- e- from NADH are transferred to flavin mono nucleotide (FMN) in complex I reducing it to FMNH2
- e- are then transferred to a series of iron clusters which are prosthetic groups in complex 2
- flow of e- through complex I results in 4H+ pumped into the inner mitochondrial space
- e- from complex II flow through complex III which results in the pumping of another 4H+
- transfer of e- through complex IV leads to the pumping of 2H+
what is chemiosmotic hypothesis?
it proposes that e- transfer directly produces an electrochemical gradient of protons across the coupling membrane that is subsequently used to drive ATP synthesis
for each pair of e- transferred to O2 from NADH, 10H+ are pumped into the intermmembrane space! this creates an electrical gradient since there’s more + on thecytosolic side of the membrane than the matrix side
pH gradient is also generated and the cytosolic side is at a lower pH
the energy released by these gradients aka the proton motive force, drives the synthesis of ATP = proton gradient couples oxidation to phosphorylation
what happens in complex V of the ETC?
complex V = ATP synthase
H+ pumped out re-enters the matrix by passing through ATP synthase channel to neutralize pH & electrical gradient
rotation of C ring of the protein channel caused by the movement of protons causes conformational changes in the 3 beta subunits of F1 that allows them to bind to ADP, phosphorylate it and subsequently release this ATP
where are the electron carriers of the ETC located?
in the inner mitochondrial membrane
