Question

cyanide (cn-) is an inhibitor of the electron transport chain (etc). however, the addition of cn- to the mitochondria not only inhibits the etc but also inhibits atp synthesis (bottom line on the above graph). explain the reason for this.

Answer 1

Cyanide inhibits cytochrome c oxidase in the ETC, causing the pH of the intermembrane space to increase and subsequently inhibiting ATP synthesis due to disruption of the proton gradient required for chemiosmosis.

Step-by-step explanation:

Cyanide is a potent inhibitor of the electron transport chain (ETC) as it binds to cytochrome c oxidase (Complex IV), which is essential for the electron transport process that drives oxidative phosphorylation. When cyanide poisoning occurs, the activity of the ETC is interrupted, leading to a cessation in the pumping of protons (H+) across the mitochondrial membrane. Consequently, this would lead to an increase in pH in the intermembrane space as the proton gradient dissipates. The proton gradient is crucial for ATP synthesis; it is used by ATP synthase as a driving force to convert ADP to ATP (a process known as chemiosmosis). Therefore, with an inhibition of the proton gradient formation due to cyanide, ATP synthesis is inhibited, affecting cellular energy production.