You incubate isolated intact mitochondria in a buffered solution containing succinate (an oxidizable substrate) and ADP plus Pi. Upon adding cyanide (an inhibitor of Complex IV, cytochrome c oxidase), you examine the effect on oxygen consumption and the production of ATP. What will occur?

Answer: "cyanide interferes with the reduction of oxygen, which decreases the proton gradient and ATP production."

Explanation:

The electron transport chain is an energy converter, transforming chemical energy to the energy of a proton gradient. As electrons flow along their energy gradient, some of the energy used by each complexes (NADH dehydogenase, cytochrome b-c1 and cytochrome oxidase a-a3) to pump proton from the mitochondrial matrix into the intermembrane space. This creates a proton gradient which in turn drives them back across inner membrane through ATP synthase, which uses the energy of H + flow to synthesize ATP from ADP and Pi.

When cyanide is added, it inhibits cytochrome c, one of the complexes responsible to transfer electrons along the chain. Hence electron transport chain will become nonfunctional. Oxygen will not be reduced. And since the electron transport chain will be nonfunctional, no proton gradient will be available to drive ATP synthase to synthesize ATP from ADP and Pi, so no ATP will be produced.

No Oxygen will be consumed, and there will also be no ATP production.

Explanation:

No Oxygen will be consumed, and there will also be no ATP production.

The blockage of the binding of Oxygen with cytochrome C enzyme occurs, and this greatly decreases the cellular uptake of oxygen.

Therefore, in the presence of cyanide, ATP production is inhibited due to blocked oxygen utilization.