Biochemistry Lecture 4: Proton Motive Force (PMF) and ATP Synthesis

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Proton Gradient
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A form of Conserved Energy Transfer
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Proton Motive Force (PMF)
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-Generated as a result of proton transport -Has 2 Compartments pH gradient Voltage Gradient -Membrane is Impermeable to protons except through specific transporters
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ATP Synthase
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Enzyme involved in ATP synthesis: -Catalyses phosphorylation of ADP -It is largely involved in controling the flow of protons going *BACK* into the matrix -Potential energy of proton gradient/electrical gradient is *converted* into chemical energy of ATP
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ATP Reactants
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ADP + Pi and Energy stored in PMF
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Chemiosmotic Theory
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Transmembrane diference in proton concentration are the reservoir for the energy extracted from biological oxidation reactions. This energy is then stored as a transmembrane difference in charge and pH , which drives the formation of ATP in *oxidative phosphorylation*
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Structure of ATP Synthase
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Contains 2 Components F0 and F1 -F0 Across membrane -F1 Facing membrane -F1 alone has no ATP Synthase activity -F0 provides the proton channel
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Adenine Nucleotide Translocase
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An *Antiporter* that transports both ATP and ADP -ADP moves into the mitochondira, ATP moves out of the mitochondria -ADP has -3 negative charge and ATP has -4 negative charge
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Phasephate translocase
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A symporter that transports both Pi and H+
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Electron Transport and ATP Syntheis Tightly Linked
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-O2 consumption and ATP synthesis are monitored and seen to be linked through oxidative phsophorylation
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Control of Oxidative Phosphorylation
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ATP synthesis is regulated by energy needs of the cells (ADP levels regulate ATP Synthesis) -Resting Respiration -Active Respiration
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Resting Respiration
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-Low [ADP] -Very High Mass action ratio -High Energy state of the cell
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Active Respiration
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-High [ADP] -Low Mass action ratio -Very low Energy state of the cell
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Mechanical Damage to Inner Mitochondrial Membrane
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Results in *Uncoupling of Mitochondria*. This is where: -Proton Gradient is abolished -Electron Transfer occurs but no phosphorylation
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Chemical Damage to Inner Mitochondrial Membrane
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Results in *Uncoupling of Mitochondria*. This is where: -Proton gradient is discharged , resulting in *NO* driving force for ATP synthesis
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Inhibitors of ATP Synthesis
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Inhibits ATP synthase by blocking protein channel F0. These Inhibitors are: -Oligomycin -Venturicidin
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Natural Uncouplers
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Found in Brown Fat deposits of new-born mammals -Rich in mitochondria and Cytochromes
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Thermogenin
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An uncoupling protein that is an integral part of the Inner Mitochondria Membrane. It: -Provides alternative Proton Channel -Promotes energy as heat for temperature maintenance

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