Cell Bio Lecture Notes #32 p.672-684
Phospholipid vesicle, bacteriorhodopsin, ATP synthase generate ATP.
3H+ into mitochondrial matrix = 13.8 Kcal/mol at PMF of 200mV.
If PMF drops to 160 mV, ATP will be hydrolysed to increase PMF.. Same interconvertibility for
Ca+ , Na+-K+pumps.
O2 injection into mitochondrial suspension causes brief respiratory burst and acidification of medium. Submitochondrial particles (inside out) causes brief drop (alkaline) in pH.
Cytochromes = heme held by 4 nitrogens, Fe+3 (ferric) to Fe+2 (ferrous) when e- added. Porphyrin rings in red blood (iron of hemoglobin), green leaves (magnesium in chlorophyll).
Iron-sulfur centers and ubiquinone (CoQ), copper atoms and a flavin (40 proteins total) also carry electrons along membrane from NADH to oxygen.
3 respiratory enzyme complexes involved: 1. NADH dehydrogenase(22polypep.) 2.b-c1 complex (8 polypep.) 3.cytochrome oxidase (dimer of 9 polypep./monomer)
NADH donates 2e-, each O2 requires 4e-, several carriers only handle 1e-, so, several e- collecting, dispersing pts.
One e- onto O2 causes O2- (superoxide) formation; extremely reactive (reason strict anaerobes can't tolerate any O2.
e- handed off by random collisions (unlike many metabolic pathways). Most negative redox potential = greatest tendency to donate electrons; most positive hold on to electrons.
NAHD dehydrogenase and b-c1 pump 2e- H+ per e-; cytochrome oxidase pumps 1. Study various electronegativities in liposomes + individual complexes + exogenously supplied redox couples.
Uncouplers like DNP dissipate PMF, so, o2 used, sugars used, no ATP made. Great diet pill? Cataracts, death = side effects…
Electron transport, ATP synthase similar equilibrium processes; controlled by concentrations of reactants, products.
Uncouplers in "brown fat" allow heat, not ATP generation. Arctic duty keeps fat away! Some fat harder to catabolize in different sexes.
Bacterial "variations on theme" use Na+ instead of protons to make ATP, use glycolysis anaerobically to makew ATP, use ATP to create H+ gradient. Use H+ gradient for transport, etc.
Note: p. 679 should read, "...exploited to pump protons (not proteins) out of the mitochondrial matrix."(about the only error in this text!)