Oxidative Phos - Abali 3/7/16 Flashcards
why do we need oxygen?
what types of work are driven using energy from ox phos?
required for total oxidation of glucose; oxygen is fully reduced to pick up the electrons given off in that process
- mechanical work (muscular contraction)
- chemical work
- transport work
oxidative phosphorylation
- parts
- process
two parts
1. electron transport chain :
- electrons are donated by NADH molecules (generated from metabolism of food)
- drives Complexes I, III, IV to pump H into intermembrane space
2. chemiosmosis :
- H gradient generated by etc - proton motive force - that drives Complex V (ATP synthase) to pump H back out and turn ADP into ATP
2 processes that generate ATP
- % of ATP generated
- how does the process sustain itself (NAD+)
glycolysis
- 10% of ATP
- NAD+ regenerated via anaerobic production of lactate [lactate dehydrogenase]
oxidative phosphorylation
- 90% of ATP
- NAD+ regenerated via donation of e to electron transport chain by NADH
overall role of cardiopulm system in context of biochemical processes
- two biochemical scenarios that potentiate O2 delivery in tissues
cardiopulm system provides the transport mechanism (blood/Hb as carriers, heart as the motor, lungs as dropoff/pickup vehicles) to move…
- CO2 waste products of TCA cycle
- O2 required for oxphos
O2 delivery is enhanced in conditions of…
- 2,3BPG buildup (intermediate of glycolysis)
- low pH
functional parts of the mitochondria and what they contain
outer membrane
- contains porins, permeable up to 10kDa
intermembrane space
- generally low pH (if etc is doing its thing)
- location of apoptotic molecules (triggered by cyt c)
inner membrane
- impermeable to everything but H2O, O2, CO2, NH3
- everything else passes through transport shuttles
- Complexes I, II, III, IV, V + CoQ making up the respiratory chain needed to generate proton motive force
mitochondrial matrix
- generally high pH
- pyruvate dehydrogenase
- TCA cycle enzymes (all except succinyl dehydrogenase/Complex II - FADH2 generator - which is in inner membrane)
- FA beta ox enzymes
- some urea cycle enzymes (protein metab)
redox reactions: players
oxidation (LEO, OIL)
- reductant loses electrons = gets oxidized
- facilitated by an oxidizing agent
reduction (GER, RIG)
- oxidant gains electrons = gets reduced
- facilitated by a reducing agent
how is energy harvested through the etc?
NADH/FADH2 act as reductants, deliver electrons to etc
- high e electrons lose energy in several steps, which allows energy to be siphoned off for use in ATP generation (instead of rapidly dissipated as heat)
practical meaning of high/low ΔEo’
- low ΔEo’ = willing to lose electrons (low affinity for e), be oxidized
- high ΔEo’ = willing to pick up electrons (high affinity for e), be reduced
relative efficiency of oxphos
approx 40% of energy that goes through oxphos is captured to generate ATP
other 60% is lost as heat
relatively efficient!
breakdown of oxphos complexes and their critical components
Complex I (aka NADH dehydrogenase)
- Fe-S center
- FMN
Complex II (aka succinate dehydrogenase)
- Fe-S center
- uses FAD/FADH 2 to pump e to CoQ
- generates less ATP bc it doesnt contribute to the proton gradient!
Coenzyme Q (aka Q10, CoQ, ubiquinone)
- hydrophobic/lipophilic molecule in inner membrane
Complex III (aka cytochrome c reductase)
- Fe-S center
- Cyt b
- Cyt c1
cytochrome c
- water soluble; moves in vicinity of outer face of inner membrane, shuttling electrons one at a time from Complex III to Complex IV
Complex IV (aka cytochrome c oxidase)
- Fe, Cu
- Cyt a
- Cyt a3
- transfers 2 e to 1/2 O2: catalyzes 1/2O2→H2O
Complex V (aka ATP synthase, F0/F1 ATPase)
- F0: transmembrane proton pump, inhibited by oligomycin
- F1: ATP synthesizer
stops on etc for an electron
NADH → complex I → CoQ → complex III → cyt c → complex IV → O2
on their journey from NADH to oxygen, e stop at…
- 4 protein complexes in inner mito membrane: I, II, III, IV
- 2 mobile carriers
- lipid soluble CoQ (inner mito mem)
- water soluble cyt c
overall, releases energy used for ATP synth and generates water
NADH
- role
- where it comes from
NADH carriers e obtained from metabolism through glycolysis and/or TCA cycle to the etc
- if obtained from glycolysis, NADH is in cytosol
- has to be transported in via _____
- if obtained through TCA cycle, NADH is already in mito matrix, ready to go
bypass reactions
- definition/naming
- 3 rxns
reactions that produce FADH2, and therefore allow for insertion of 2e- into the etc at CoQ, effectively bypassing complex I
- complex II/succinate DH (inner part of inner mito mem)
- G3P DH (outer part of inner mito mem/intermembrane space)
- fatty acyl CoA DH (inner part of inner mito mem/mito matrix)
chemiosmosis and complex V
ATP synthase aka F1F0 ATPase
- F0 subunit pumps e from intermembrane space into matrix
- forces the turning of a shaft that in turn causes F1 subunit to rotate
- rotational energy allows the synthesis of ATP
prerequisites for ox phos to take place
- availability of reducing agents: NADH, FADH2
* from glycolysis, FA oxidation, TCA cycle - pH gradient (proton motive force, low pH in intermembrane space)
- terminal oxidizing agent (O2)
- high ADP/ATP ratio
- sufficient mitochondria with the enzymes and metab machinery for oxphos to take place