Question

Should Complex II (Sucinate Dehydrogenase) be considered part of the electron transport chain? If you were the first to discover the identity and function of these protein complexes, would you consider Complex II to be part of the Electron Transport Chain. Defend your answer.

Answer 1

Yes, complex II (succinate dehydrogenase) should be considered a part of electron transport system. Electron transport chain runs in inner mitochondrial membrane and all protein complex of electron transport chain is found in inner mitochondrial membrane. Succinate dehydrogenase enzyme is embedded in inner mitochondrial membrane and it reduces FAD into FADH2 by oxidising Succinate into Fumarate inside inner mitochondrial membrane.

Complex II (Succinate dehydrogenase) transfers electrons to Ubiquinone, then to complex III, complex IV and finally to final electron acceptor oxygen present in matrix of mitochondrion.

It is evident here that both Succinate dehydrogenase and protein complex of electron transport chain are embedded in inner mitochondrial membrane and work in coordination to oxidize reducing power such as FADH2.