BIOC2600 1.4

• ATP is the energy currency used by cells.
• ATP hydrolysis helps thermodynamically unfavourable reactions.
• ATP is synthesized in cells through substrate level phosphorylation and oxidative phosphorylation.
• Glucose breakdown involves glycolysis, the citric acid cycle, and the electron transport chain.
• Only a small amount of energy available in glucose is captured in glycolysis.
• Complex II: Succinate dehydrogenase.
• Succinate dehydrogenase is a single enzyme with dual roles: convert succinate to fumarate in the TCA cycle.
• The transfer of electrons from NADH to ubiquinone is accompanied by a transfer of H+ from the matrix (N) to the intermembrane space (P).
• ATP stands for adenosine 5’ - triphosphate.
• Nucleic acid is a building block of RNA.
• ATP is the most commonly used energy currency.
• Energy is released from the cleavage of the triphosphate group of ATP.
• ATP powers many cellular processes.
• ATP hydrolysis is exergonic, releasing energy.
• The free energy released from ATP hydrolysis is used to drive reactions that require an input of energy.
• 2 NADH are converted to 2 FADH 2 and fed into ETC.
• Glycerol - 3 - phosphate shuttle operates in skeletal muscles and brain.
• Therefore, 3 ATP are made from this path.
• FADH 2 + 6H + (N) + ½O 2 —— > FAD + 6H + (P) + H 2 O —— > 1.5 ATP.
• In cytosol, dihydroxyacetone phosphate accepts the reducing equivalents from NADH to form glycerol - 3 - phosphate by the cytosolic form of glycerol - 3 - phosphate dehydrogenase.
• The mitochondrial form of glycerol 3 - phosphate dehydrogenase then transfers the reducing equivalents to ubiquinone via the formation of FADH 2.
• The ATP - ADP cycle is the fundamental mode of energy exchange in biological systems.
• Coupling ATP hydrolysis with an endergonic reaction transfers energy from ATP to the endergonic reaction.
• Cellular ATP concentrations are far above the equilibrium concentrations for hydrolysis reactions.
• When ATP level drops, the amount of fuel decreases and the fuel loses its potency.
• For each pair of electrons transferred to O2, 4 protons are pumped out by Complex I, 4 protons by Complex III, and 2 by Complex IV.
• The energy released from the electron transport chain is used to pump protons (H+) out of the matrix (N side) into the intermembrane space (P side), creating a proton gradient.
• Mitochondrial ATP Synthase Complex contains two functional units: F1, a soluble complex in the matrix, and F0, an integral membrane complex.
• Complex IV: Cytochrome oxidase completes the sequence by transferring the electrons from cytochrome c to O2, reducing O2 to water.
• A proton gradient is created by the electron transport chain, with the flow of electrons from NADH or FADH2 highly exergonic (energy releasing).
• The proton gradient across the membrane generates a proton-motive force to drive ATP synthesis by ATP synthase when protons enter back to the matrix via proton-specific channels in F0.
• There are two paths of electron transport in the ETC: for electrons from NADH and for electrons from FADH2.
• The proton-motive force is the chemical gradient (ΔpH) and the electrical gradient (∆𝜓), which drive the protons back into the matrix, and provide the energy to make ATP.
• Complex III: Ubiquinone:cytochrome c oxidoreductase carries electrons from reduced ubiquinone from Complexes I and II to cytochrome c.
• The difference in the number of protons transported reflects the differences in ATP synthesized.
• The rotation of the F0 subunit and the central shaft g causes a conformational change within all the three a b pairs in F1.
• Proton translocation causes a rotation of the F0 subunit and the central shaft g.
• Complex II transfers FADH2 + 6H+ (N) + ½O2 → FAD+ 6H+ (P) + H2O, resulting in 1.5 ATP.
• ATP synthase in action.
• ATP synthase couples proton translocation to ATP synthesis.