Electron Transport Chain
ELECTRON TRANSPORT CHAIN
- Complex I: NADH dehydrogenase
- aka NADH-CoQ reductase
- NADH delivers 2 electrons to the complex I and is oxidized to NAD+
- CoQ (aka Q10 and ubiquinone)
- Lipid-soluble
- Mobile carrier
- NOT a protein
- Complex II: succinate dehydrogenase
- aka Succinate-CoQ reductase
- Also part of citric acid cycle
- FADH2 delivers two electrons to complex II
- Complex III: Cytochrome bc1 complex
- aka CoQ-cytochrome c reductase
- Cytochrome C
- Water-soluble
- Mobile carrier
- Complex IV: cytochrome c oxidase
- Produces one H2O from 2 H+ plus ½ O2 + 2e-
- Complexes I, III & IV pump H+ from matrix to intermembrane space
REDOX REACTIONS
- NADH (2e-) reduces complex I
- FADH (2e-) reduces complex II
- CoQ (mobile carrier) transports 2e- from complex I & II to complex III
- Complex III (simplified diagram): Cyt. B & Cyt. C1 are e- transport proteins
- Cyt. C1 donates 2e- (1e- at a time) to Cyt. C (mobile-carrier)
- Cyt. C transports 4e- to complex IV (2 molecules of Cyt. C deliver 2e- each)
- Complex IV (simplified diagram w/o Cu centers): Cyt. A (4e-) to Cyt. A3 (4e-) to oxygen
- Oxygen (final e- acceptor) 4e- + 4H+ (from matrix) + O2 --> H2O