OXIDATIVE PHOSPHORYLATION 9/25/07

ATP _ Universal Carrier of Free Energy _ Chemical _ Ionic Provides Energy for: _ Mechanical Work

Role of ATP in Metabolism Know this structure It is the most important molecule in biochemistry.

The Concept Energy rich molecules donate electrons to specific coenzymes to form energy-rich reduced coenzymes 1 pair of electrons is donated per each reduced coenzyme H 2 = H + H H = 1 electron + 1 proton :H ¯ = 2 electrons + 1 proton (Hydride ion) + H + = 1 proton These electrons are donated to the electron transport chain to form ATP

Electrochemical gradient Oxidized Reduced

Glycolysis Cytoplasm Electron Transport Inner mitochondrial membrane Is the final common pathway by which electrons from food molecules are used to make ATP and molecular oxygen acts as the final acceptor of the electrons Carriers and transport systems are used to move ions and molecules across this membrane Membrane convoluted or folded = ↑ Surface Area (Cristae) Contains the ATP Synthetase complex ATP Synthetase complex 50% protein

NADH Dehydrogenase Citric acid cycle 2 e¯ Citric acid cycle 2 e¯ Final acceptor of e - s is molecular oxygen Cytochrome oxidase (Iron + copper) Complex V contains ATP Sythase Series of Oxidation/Reduction reactions Electron transport chain ▬ 3 components Flavoprotein ▬ NADH Dehydrogenase CoQ (Quinone) ▬ Ubiquinone Cytochromes ▬ Heme group ▬ Iron ▬ Ferric (Fe 3+ ) ▬ Ferrous (Fe 2+ )

Each one of these inhibitors will completely stop electron transport and thus all ATP production Cyanide

Three Main Tenets of the Mitchell Theory

ATP Synthase This dissipates gradient Blocked by atractyoside (Plant toxin) FADH 2 FAD + Lower pH pH gradient Oligomycin blocks ADP ATP More protons Electrical gradient 1 NADH = 3 ATP 1 FADH 2 = 2 ATP Chemiosmotic Hypothesis of Electron Transport coupled to ADP Phosphorylation ▬ “Mitchell Hypothesis” Features: Protons transported from the matrix to the inner mitochondrial space results in an electric gradient and a pH gradient As the protons flow through the membrane channel back into the matrix they drive ATP synthesis Occurs with energy utilized by ATP synthase This proton transport couples electron transport to oxidative phosphorylation Cytoplasm

Uncoupling of Oxidative Phosphorylation Electron Transport ADP ATP ADP ATP ADP ATP O2O2 H2OH2O Electron transport coupled to phosphorylation of ADP  ATP Electron Transport O2O2 H2OH2O + Dinitrophenol (DNP) breaks down proton gradient High doses of aspirin ▬ results in fever Introduced in 1932 as weight reduction drug = Fatal hyperthermia Electron transport continues No ADP phosphorylation Energy dissipated as heat HEAT

Brown adipose tissue creates heat by thermogenesis Thermogenin = uncoupling protein ▬ UCP1 The energy is given off as heat Mechanism is to ↑ FA oxidation which uncouples oxidation phosphorylation Breaks down proton gradient

Inherited Diseases of Oxidative Phosphorylation LIBER’S HEREDITARY OPTIC NEUROPATHY Bilateral loss of central vision occurs because of Neuroretinal degeneration Mutation in mitochondrial DNA Mitochondrial DNA is maternally inherited because all mitochondria come from the mother None come from the sperm because none from sperm enter the egg during fertilization Some mitochondrial myopathies caused by mutations in mtDNA 13 of the ~100 proteins in the mitochondrion are coded for by mtDNA Has mutation rate > 10x that of nuclear DNA

Malate-Aspartate shuttle 3 ATP for each NADH Glycerophosphate shuttle 2 ATP for each NADH transported into mitochondrion from the cytoplasm

Shuttle systems to bring cytosolic NADH into mitochondria for oxidative phosphorylation 1) Glycerophosphate shuttle = 36 ATP 2) Malate-aspartate shuttle = 38 ATP Count ATPs: Anerobic glycolysis = 2 Glycolysis + CAC + oxidative phosphorylation = 38 NADHFADH 2 ATP 1Glycolysis2 2Glycolysis (G-3-P  1,3,BisP)26 3Pyruvate  Acetyl CoA26 4, 5, 6CAC618 7CAC-FADH CAC – substrate level ATP2 Total38

Revolves at 100 Hz (revolutions/s) This is sufficient to produce a turnover of The weight of our body of ATP each day! ATP synthase: 2 Domains F1F1 F0F0 Rotates in 120° stages 100 Hz one complete revolution = 3 ATP Need 10 H + 1 ATP = 3.3 H +...