Answer:
The electron transport chain consists of a series of redox reaction in the form of complex I, Q, complex II and III.
1- complex I establishes hydrogen gradient across the matrix by transferring two hydrogen ions plus its uses FMH as a cofactor.
2- In Q and complex II series, Q is reduced by NADH into QH2 and this complex receives FADH2 which delivers electrons to ETC.
3- The third complex is composed of cytochrome b and c.It also transfers protons to the fourth complex.
4- The Fourth complex contains cytochrome proteins c, a, and a3. It reduces oxygen which picks up the protons to form water.
Overall series of reactions in ETC:
NADH+H+ → Complex I → Q → Complex III → cytochrome c → Complex IV → H2O
↑
Complex II
↑
Succinate
Respiratory chain:
1- Hydrogen is obtained by the reduction of NADH and from FADH.
2- The electrons are transferred to complexes I, II and III and then to oxygen.
3- After this complexes, I, II and III expel protons across the membrane.
4- These protons are then used to synthesize ATP.