From Bioblast
The membrane-bound electron transport system (ETS) consists in mitochondria mainly of respiratory complexes CI, CII, electron transferring flavoprotein (ETF), glycerophosphate dehydrogenase (GpDH), and choline dehydrogenase, with convergent electron flow at the Q-junction (Coenzyme Q), and the two downstream respiratory complexes connected by cytochrome c, CIII and CIV, with oxygen as the final electron acceptor.
References
Gnaiger E (2009) Mitochondrial pathways through Complexes I+II: Convergent electron transport at the Q-junction and additive effect of substrate combinations. Mitochondr. Physiol. Network 12.12: 1-20.