<prompt> Cyanide is toxic because itInhibits cytochrome oxidaseForms cyan meth HbInhibits ATP carrier in mitochondriaInhibits Na-K-ATP ase  <response>: Site-III Complex IV CYTOCHROME OXIDASE Cyanide Blocks electron transfer from cyt b to c1 Inhibits terminal H2S Azide transfer of electrons to molecular O2 Co Carbon monoxide: Inhibits Cyt. oxidase by combining with O2 binding site. It can be reversed by illumination with light.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th Edition 