BIOC192 Lecture 32 - Electron Transport Chain Flashcards
how is the electron transport chain organised?
organised into four complexes: I to IV
how many carriers does each complex contain?
each complex contains multiple carriers
what are the 2 mobile carriers?
1) UQ and CoQ (both the same thing just different names)
2) cyt c (cytochrome c)
what is the relationship between carriers and redox reactions?
each carrier accepts electron(s) (is reduced) in one redox reaction and then donates electron(s) (is oxidised) in another redox reaction
how is energy released in the electron transport chain?
as electrons move through the carriers, energy is released
what is the relationship between electron moving to carriers and reduction potential?
electrons move to carriers with a higher reduction potential
what molecule has the highest reduction potential?
oxygen
what is the function of releasing energy in the electron transport chain?
the energy released in the electron transport chain is used to translocate proton across the mitochondrial inner membrane
what is the electron flow through the electron transport chain of NADH?
complex I –> UQ –> complex III –> cyt c –> complex IV –> O2
what is the electron flow through the electron transport chain of FADH2?
complex II –> UQ —> complex III –> cyt c –> complex IV –> O2
what is the function of rotenone?
inhibits the transfer of electrons from complex I to Co-Q
what is the function of cyanide?
binds to a carrier in complex IV
what is the function of carbon monoxide?
binds where O2 binds
what are the 3 inhibitors of electron flow through the electron transport chain?
1) rotenone
2) cyanide
3) carbon monoxide
what are the 4 effects of inhibitors of electron flow through the electron transport chain?
1) stop flow of electrons through the ETC
2) build-up of reduced co-enzymes (NADH and FADH2)
3) no proton gradient formed
4) reactive oxygen species produced cause damage to cells
what is the electron flow through the ETC in complex I?
- NADH is oxidised at complex I
- 2 electrons release into the ETC
- 4 protons are pumped for each NADH oxidised
what is the electron flow through the ETC in complex II?
- FADH2 is oxidised at complex II
- SDH reaction is shared with the citric acid cycle
- 2 electrons released into the ETC
- no protons are pumped
what is the electron flow through the ETC in UQ?
- complex I and complex II both pass 2 electrons to UQ/CoQ
- UQ can move within the inner mitochondrial membrane
what does Co-Q under?
undergoes 2-electron redox reactions (like NADh and FADH2) but can accept/release 1 electron at a time
what is the electron flow through the ETC in CoQ?
- complex I and complex II both pass 2 electrons to CoQ
- CoQ releases 1 electron at a time to complex III (Q-cycle)
what is the electron flow through the ETC in complex III?
- complex III releases 1 electron at at time to cytochrome c
- complex III pumps 4 protons across the inner membrane (for 1 coenzyme/ 2 electrons)
what is the electron flow through the ETC in cytochrome c?
- moves on outer surface of the inner mitochondrial membrane
- cytochrome c carries 1 electron at at time from complex III to complex IV
what is cytochrome c?
cytochrome c is a heme containing protein
-carries 1 electron via reversible Fe2+/Fe3+ redox reactions
what is the electron flow through the ETC in complex IV?
- complex IV accepts 1 electron at a time from cytochrome c
- reduces oxygen to water (terminal electron acceptor)
- for 1 NADH/FADH2 (2 electrons): 2 H+ pumped
- for 1 NADH/FADH2 (2 electrons): 1/2 O2 + 2 H+ –> H2O
what happens biologically in complex IV?
the last carrier in complex IV waits until it has 4 electrons O2 + 4H+ –> 2H2O
is there any movement between complex I and complex II?
no
how many protons are pumped from NADH?
10 protons pumped
how many protons are pumped from FADH2?
6 protons pumped
