<prompt> Which of the component of respiratory chain reacts directly with molecular oxygen?Cyt bCoQCyt CCyt aa3  <response>: Complex IV: Cyt-c Oxidase The system functions: As proton pump Catalyses transfer of electrons to molecular O2 to form H2O. This is the terminal component of ETC. It catalyses the transfer of electrons from Cyt-c to molecular O2 Cyt-a, Cu ions and Cyt-a3.Ref: MN Chatterjea Textbook of Medical Biochemistry, 8th edition, page no: 142 