Mechanism of action of cyanide: Cyanide acts as an irreversible inhibitor of the
ID: 96004 • Letter: M
Question
Mechanism of action of cyanide: Cyanide acts as an irreversible inhibitor of the electron transport chain; specifically it blocks cytochrome oxidase which catalyzes the transfer of electrons from cytochrome a3 of complex IV to molecular oxygen during the final reaction of the electron transport chain. Questions: 1. Based on the above mechanism of action of cyanide and what you know about the role of oxygen in aerobic cellular respiration, predict what you would expect if you conducted an experiment in which you examined the effect of cyanide on oxygen consumption. Would oxygen consumption increase, decrease slightly, or be completed halted? What would happen to ATP production: would ATP produced by chemiosmosis increase or decrease, would it eventually halt? Explain. 2. Now, comment on whether the effect of cyanide on cellular respiration can be bypassed. Based on what you learned about oxidative phosphorylation in your lecture textbook and during this laboratory, can you bypass the effect of cyanide (which you determined under question 1) by increasing the amount of any substrate of cellular respiration? Explain. 3. Next, consider the following experiment: You isolate whole mitochondria with cristae from cells. In the presence of cyanide, you first place these mitochondria into a slightly acidic solution, and then you transfer them into an alkaline solution. You subsequently observe production of small amounts of ATP. Explain why the change in pH of the environment resulted in the production of small amounts of ATP by oxidative phosphorylation and thereby temporarily bypassed the effects of cyanide (hint: think about the flow of hydrogen ions across mitochondrial cristae). 4. Finally, consider the following experiment: You repeat the experiment under question 3. Except now, you also add oligomycin to your reaction flask. After you change the pH of the environment, you no longer observe production of ATP. Mechanism of action of oligomycin: Like cyanide, oligomycin is an oxidative phosphorylation inhibitor – except that it acts on a different step of oxidative phosphorylation. Oligomycin specifically binds to an F0 protein of the F 0 F 1 complex (also called the ATP synthase), and thereby inhibits the flow of hydrogen ions through this pump.
Explanation / Answer
When we talk about aerobic respiration,cyanide on oxygen consumption reduces the rate of oxygen and hence blocks the process of cellular respiration.
Electron transport chain is the final stage of cellular respiration.As a effect of cyanide the oxygen molecule is not able to bind with the molecule which results in breaking the process of ETC therefore Development of ATP molecules that are energy molecules stops.