Oxidative Phosphorylation Flashcards
ATP is the principal _________ molecule in living organisms
Free energy currency
Dephosphorylation reaction
highly spontaneous, releases large amount of free energy (exergonic)
What is often coupled to vital, non spontaneous reactions to drive them forward?
ATP hydrolysis
ATP resynthesis is highly _______
endergonic
______ has to be synthesized at about the same pace it is consumed
ATP
Glycolytic Pathway
does not require oxygen; inefficient way to produce ATP;
transports reducing equivalents from glycolysis to ETC;
end product is pyruvate
Malate-Aspartate Shuttle
IMM is impermeable to NADH; permits transfer of NADH from glycolysis into the mito matrix; glutamate oxaloacetate transaminase turns oxaloacetate into aspartate to cross IMM; malate dehydrogenase (present in cytoplasm and mito matrix) converts oxa into malate to enter TCA
Where does Oxidative Phosphorylation take place?
Mitochondria;
3D network that is highly dynamic
Outer mito membrane is permeable to small molecules/ions through
Porins
Inner mito membrane
rich in proteins;
site of OxPhos;
impermeable;
cristae for increased surface area
Mitochondrial matrix
TCA;
b-oxidation;
basic pH;
mtDNA
Chemiosmotic Theory
- Electron transport drives proton pumping
- O2 is final electron acceptor (H2O)
- Pumping protons out of matrix creates electrochemical gradient
- Electrical gradient + pH gradient = proton motive force
- Protons flow down the gradient into matrix; drives ATP synthesis (dependent on ADP availability)
ATP synthesis is _____ driven
demand; synthesis only if ADP demands it
Oxidation-reduction definition
removal and addition of electrons
Oxidoreductases
transfer e-from one molecule to another
Dehydrogenase
remove hydrogen from the electron donor
Strong reducing agent
wants to give away electrons
strong oxidizing agent
wants to take electrons
NAD (nicotinamide adenine dinucleotide)
NADH (reduced form)
electron/hydrogen carrier derived from niacin;
involved in several ox/redux reactions catalyzed by dehydrogenase;
NADH enters ETC at complex I;
Oxidized by ETC to produce 2.5 molecules of ATP
FAD - Flavin Adenine Dinucleotide
FADH2 (reduced form)
Electron/hydrogen carrier derived from riboflavin;
FADH2 produced by complex II and other flavin electron transfer proteins;
Oxidized by ETC to produce 1.5 molecules of ATP
Reduction Potential
tendency of the oxidized species of a redox couple to accept e- (become reduced)
Complex I
NADH-Co-Q oxidoreductase;
e- transfer via FMN and Fe-S cluster;
pumps 4H+ per e- pair
Complex II
Succinate dehydrogenase;
FAD-linked e-transfer;
Fe-S cluster;
NO PROTON PUMPING
Ubiquinone (oxidized form) Ubiquinol (reduced form)
Resides in lipid bilayer;
passes its e- to cytochrome c via the actions of complex III in a process called Q cycle
Complex III
Co-Q-cytochrome C oxidoreductase;
electron transfer via heme prosthetic groups and Fe-S cluster;
Pumps 4H+ per e- pair
Cytochrome C
mobile e- carrier that shuttles e- to complex IV (resides in IMS)
Complex IV
cytochrome c oxidase;
electron transfer via heme and Cu;
pumps 2H+ per e- pair;
additional 2H+ used to reduce O2 to water
Complex V
site of ATP synthesis; energy from PMF used to generate high energy phosphate bond as H+ ions descend the concentration gradient across the IMM
ATP synthase (complex V) synthesizes ATP by…
rotary motar mechanism that requires a proton gradient and ADP binding;
(NO ADP = NO proton influx);
Proton influx through channel drives rotation and conformational change;
each 360 deg turn requires 10 protons and produces 3 ATP (3 protons per ATP)
ATP cannot be released from the synthase unless
ADP and Pi are bound at the other site
Molecule that imports ADP and Pi into matrix for ATP production (3+1 protons, 1 influx during import)
Adenine Nucleotide Translocate (ANT)
P/O Ratio
ratio of ATPs formed per mole of oxygen reduced
Physiological Uncoupling
uncoupling of e- transport and ox-phos occurs in animals as a means to produce heat (non shivering thermogenesis)
Physiological uncoupling occurs mainly in…
Brown adipose tissue (rich in mitochondria)
Uncoupling protein (UCP)
channel to allow influx of protons to matrix (dissipates proton gradient);
results in increased substrate catabolism (produces more NADH and lowers ROS production)
