Essential Elements of Biochemistry BCHM 3050 Dr Srikripa Chandrasekaran Lecture 4 15 15 Notes Respiratory Electron Transport continued I Electron Transport in Relation to Reduction Potentials A 1 molecule of glucose produces 2 NADH glycolysis cytoplasm 2 NADH pyruvate processing 6 NADH TCA 2 FADH2 TCA electrons from NADH go to Complex 1 electrons from FADH2 go to Complex 2 all electrons are then transferred to ubiquinone and transferred to Complex 3 then Complex 4 Inner membrane is where all of the electron transport is happening B NADH lowest reduction potential C Oxygen highest reduction potential D Cytochrome C is a mobile molecule E F CoQ accepts electrons from Complex 1 and 2 Some Poisons are Inhibitors of Respiratory Electron Transport A Some poisons are inhibiters B You should not consume rat poison because it acts on eukaryotes C Antimycin blocks electron transfer within Complex 3 D Cyanide prevents electron transfer from copper to oxygen kills you if E Barbituate truth serum inhibits transfer of electrons from Complex consumed 1 to Complex 2 F Rotenone is a fishacide used to kill fish if it is washed out into the sea or rivers the fish die if fish consume it and then humans consume those fish it can have harmful effects on humans G Antimycin prevents electron transport between cytochrome proteins in Complex 3 H Carbon monoxide cyanide and azide inhibit electron transport between Complex 4 and oxygen I These plants are insensitive to cyanide J These cyanide insensitive plants have an alternate oxidase instead of Complex 3 and 4 which prevents cyanide from harming them Functions of the Alternate Oxidase System A Some amount of heat is always lost B In alternate oxidase systems less protons are accumulated because the protons from Complex 3 and Complex 4 are not accumulated since these complexes are not present C For every 1 NADH 10 protons are accumulated D Severe odor of sulfur is given off by these cyanide insensitive plants Aerobic Respiration ATP Synthesis A For every 1 NADH that gives up its electrons in the electron transport chain about 2 5 molecules of ATP are harvested II III IV 1 V VI VII B For every 1 FADH2 that gives up its electrons in the electron transport chains about 1 5 molecules of ATP are harvested C About 28 molecules of ATP are accumulated from the electron transport chain 10 NADH x 2 5 ATP 25 ATP 2 FADH2 x 1 5 ATP 3 ATP 25 ATP 3 ATP 28 ATP D 4 ATP came from substrate level phosphorylation 2 ATP from glycolysis 2 ATP from TCA 4 ATP E 28 ATP 4 ATP 32 ATP F About 32 molecules of ATP for every 1 molecule of glucose ATP Synthesis Terminology A Substrate level phosphorylation occurs in the cytoplasm for glycolysis B and in the mitochondria for Kreb s Cycle In the Kreb s Cycle succinyl CoA synthetase is the enzyme that does substrate level phosphorylation Free Energy Drop at Three Sites Is Sufficient to Account for ATP Synthesis A There are several steps along the way in which energy is released and cane be used to harvest ATP Three Sites in Electron Transport with Sufficient Energy Yield for ATP Synthesis A 1 NADH that is present in the mitochondria becomes NAD H e 4 protons from Complex 1 4 protons from Complex 3 2 protons from Complex 4 10 protons total accumulate in the inner membrane space B Complex 2 is a succinate dehydrogenase complex C Complex 2 is where the electrons are given up D 1 FADH2 becomes FAD 6 protons total accumulate in the inner membrane space VIII E Protons are the force that will generate ATP Stoichiometry of Respiratory Electron Transport A Every time electrons transfer protons accumulate in the inner B As NADH and FADH2 send their electrons more and more protons C 104 protons accumulate in the inner membrane space for every 1 membrane space accumulate molecule of glucose D 8 NADH from the mitochondria give 80 protons H 2 FADH2 give 12 protons H 2 NADH in the cytoplasm give 12 protons H E 80 protons 12 protons 12 protons 104 protons total that accumulate in the inner membrane space 2
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