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Stage 4: Electron Transport Chain
Located on the inner membrane of the mitochondriaUses NADH and FADH2
5 components to the ETC ordered by increasing electronegativity
Wednesday, October 18, 17
NADH Dehydrogenaseweakest attractor of electrons in the chainNADH → NAD+ + H+ +2e-
H+ get pumped across the membrane into inter-membrane space2e- get transferred across the chainNAD+ travels back to the Krebs cycle to be recycled
Wednesday, October 18, 17
Cytochrome b-c1 Complex
Carries 2e- to cytochrome CUses the energy from 2e- to transport a second more H+ ion into the inter-membrane space of the matrix
Wednesday, October 18, 17
Cytochrome Oxidase Complex
Accepts 2e- from cytochrome CFinal H+ ion pumped across the matrix
Wednesday, October 18, 17
The role of oxygen
Oxygen acts as the final electron acceptor, the most electronegative.O2 splits and combines with free H+ in the matrix to form H2O
Wednesday, October 18, 17
The role of oxygen
Without oxygens electrons pile up, no more H+ pumped across, no more energy created
Wednesday, October 18, 17
NADH vs FADH2
NADH transfers electrons to NADH dehydrogenase, results in 3 H+ being pumped acrossFADH2 transfers electrons at ubiquinone, results in 2 H+ being pumped across
Wednesday, October 18, 17
ChemiosmosisETC create a concentration gradient of H+ ions between mitochondrial membranesATP synthase pumps H+ back into the matrix
each time H+ is pumped, free energy is available to create an ATP
Wednesday, October 18, 17
Total ATP CountGlycolysisGlycolysis
Pyruvate Oxidation
Krebs CycleKrebs CycleKrebs Cycle
2 ATP2 ATP2 NADH2 NADH
2 ATP2 ATP6 NADH2 FADH2
Wednesday, October 18, 17
Total ATP CountGlycolysisGlycolysis
Pyruvate Oxidation
Krebs CycleKrebs CycleKrebs Cycle
2 ATP2 ATP2 NADH2 NADH 6 ATP
2 ATP2 ATP6 NADH 18 ATP2 FADH2 4 ATP
Wednesday, October 18, 17
NADH is impermeable to the outer membrane of the mitochondria.
Therefore the NADH created in glycolysis is ‘handed off’ to FADH2 via a channel
Wednesday, October 18, 17
Total ATP CountGlycolysisGlycolysis
Pyruvate Oxidation
Krebs CycleKrebs CycleKrebs Cycle
2 ATP2 ATP2 NADH 4 ATP2 NADH 6 ATP
2 ATP2 ATP6 NADH 18 ATP2 FADH2 4 ATP
Wednesday, October 18, 17
Total ATP CountGlycolysisGlycolysis
Pyruvate Oxidation
Krebs CycleKrebs CycleKrebs Cycle
TOTAL
2 ATP2 ATP2 NADH 4 ATP2 NADH 6 ATP
2 ATP2 ATP6 NADH 18 ATP2 FADH2 4 ATP
36 ATP36 ATP
Wednesday, October 18, 17
Methods of Control
phosphofructokinaseEnzyme required in step 3 of glycolysis
Inhibited by ATP and citrateStimulated by ADP
Wednesday, October 18, 17