(A) cryo-EM structure of cyt b₆f complex (pdb 6rqf) from spinach [51]. (B) X-ray structure of cyt bc₁ complex (pdb 2qjy) from Rhodobacter sphaeroides [69]; (C) cryo-EM structure of cyt bc₁ complex (pdb 6kls) from Aquifex aeolicus [72]; (D) X-ray structure of cyt bc₁ complex (pdb 2ibz) from baker's yeast [67]. The deposited structure contains only one protomer which belongs to the crystallographic asymmetric unit. Here the dimeric structure shown was generated by applying symmetry operation; (E) cryo-EM structure of a supercomplex containing a dimeric cyt bc₁ complex and a monomeric cyt c oxidase (supercomplex III₂/IV, pdb 6giq) from baker's yeast [47]; (F) cryo-EM structure of a supercomplex containing a dimeric cyt bc₁ complex and a dimeric cyt c oxidase (supercomplex III₂/IV₂, pdb 6hu9) from baker's yeast [46].