LECTURE 12 - REDOX REACTIONS Flashcards
where does the ETC happen?
in the cristae
what is the difference between the outer vs inner membrane of the mitochondrion?
the outer membrane is porous, molecules can easily come in from the cytosol
the inner membrane is not very porous but it has transporters
where does the CAC happen?
in the mitochondria matrix
where does the energy for proton pumping come from?
comes from electron flow, which come from NADH and FADH
how many protons are pumped by each complex?
complex 1: 4
complex 2: 0
complex 3: 4
complex 4: 2
how many protons are pumped per two electrons?
per 2 electrons you have 10 protons pumped and 1 oxygen molecules turned into water
how does oxygen get all the electrons at the end?
has the highest reduction potential
every subsequent redox center has a higher reduction potential, this keeps the electrons moving
what are the different redox centers?
iron-sulfur clusters
cytochromes or flavoproteins
what does the pumping of protons inside the intermembrane space cause?
causes a disequilibrium of protons
lots inside the membrane, positive charge, and negative charge outside
this creates an electrochemical gradient, or also a proton motive force
what is the difference between the matrix and the intermembrane space and what is that equivalent to?
the difference is 150-200mV
when you take into account the size of the mitochondria, that is equivalent to a lighting bolt
which complexes donate to CoQ?
complex I and II
what does CoQ donate to?
donates to complex III and cytochrome C
what are flavoproteins?
have a flavan mononucleotide (FMN) or dinucleotide (FAD)
can accept and then donate electrons
what powers complex V (ATP synthase)?
complex V is powered by the energy released by complexes I, II and IV
what does cytochrome C do?
shovelling protein
takes electrons from complex III and than gives them to complex IV
what is complex IV?
cytochrome oxidase
the electrons from cytochrome will go to oxygen to make water
what are the metals in the ETC?
diverse array of metals like Fe, Cu and heme
the standard reduction potentials depend on the microenvironment
what is the structure and function of complex I?
- pumps 4 net protons
- made of 44 proteins, that come from 2 different genomes
- 7 of the proteins are coded in mitochondrial DNA, which means that coordination is needed between mitochondria and nucleus to make and assemble those proteins
- complex I has a hydrophobic arm (alpha helix) in the membrane
- has a hydrophilic arm which points into the matrix
- FMN is the first redox center, then it’s iron sulfur clusters, and finally ubiquinone
what does complex II do?
does not pump protons
contributes to membrane potential by feeding electrons into the Q pool
what are pathways that reduce CoQ?
- complex I
- complex II
- multiple dehydrogenases which are also FAD bound
they impinge upon ETF (electron transferring flavoprotein)
ETF also has an FAD
passes it onto ETF-QUO
which finally donates it to CoQ
succession of redox centers on different molecules
what does complex III do?
pumps 4 net protons
receives protons from ubiquinol
what are the different forms of Q?
Q=ubiquinone
QH=semi-quinone
QH2=ubiquinol
explain the Q cycle
- QH2 comes into complex 3, 2 protons are pumped
- one electron is donated to cytochrome C, the other one goes to a Q molecule to make QH
- the cycle starts again, with another QH2, and 2 protons are pumped again
- one of the electrons from the QH2 goes to cytochrome C and the other one goes to QH, which regenerates QH2
- the cycle can start again
- total 4 electrons: 2 cytochrome C and 2 to make QH2 again
- cytochrome C will donate these electrons to complex IV
how are these complexes arranged?
arranged into one super complex called the respirasome
for the same reasons as the PDC, it is more efficient that way, if they are all close together
