Question

How does cyanide inhibit cellular respiration, specifically ATP synthesis?

Answer 1

It blocks the active site of the FeS-protein in complex 4.

Explanation:

Blast from the past, as I actually worked on this complex..

In the Electron Transport Chain involved in Oxidative Phosphorylation, electrons are shuttled between 4 protein cytochrome complexes. At least the last two, ComplexIII and ComplexIV, contain metal atoms.

Complex III (and, it seems, Complex IV) contains an Iron-Sulphur protein (also known as "Rieske"-protein), in which the iron-atom "oscillates" between the Ferric and the Ferrous states, facilitating temporary acceptance of the electron(s).

Cyanide(s) bind to this `Fe` -atom, thereby rendering it inoperable.

This is literally a spanner in the works , and the result is that production of ATP stops.....