As a Forensic Pathologist, You Have Just Completed an Autopsy

As a forensic pathologist, you have just completed an autopsy of a poisoning victim. After a thorough examination, you conclude that the victim died of cyanide poisoning. You know that cyanide binds to the cytochrome oxidase complex, and therefore list the official cause of death as suffocation due to cyanide exposure. However, if you wanted to provide a more technical explanation as to the cause of death, what process was specifically inhibited directly by cyanide?

A) The formation of water from oxygen
B) All proton pumping into the intermembrane space
C) ATP synthesis
D) The oxidation of FADH₂
E) The reduction of NAD⁺