Final answer:
The symptoms of the firefighter, caused by an agent that inhibits electron transport and oxidative phosphorylation, are due to the agent combining with cytochrome oxidase, which blocks the electron transport chain and halts ATP production.
Step-by-step explanation:
The causative agent of the symptoms leading to headaches, weakness, confusion, and difficulty in breathing that the firefighter is experiencing inhibits electron transport and oxidative phosphorylation by combining with cytochrome oxidase (option C). Cyanide and carbon monoxide are known to bind with the heme group of cytochrome c oxidase, a critical component of the electron transport chain. This binding inhibits the normal function of cytochrome oxidase, preventing electron transfer to oxygen, the final electron acceptor. As a result, the oxidative phosphorylation process, which is essential for ATP production, is halted. If cyanide poisoning occurs, it would be expected that the pH of the intermembrane space of the mitochondria would increase because the normal pumping of protons (H+) across the membrane is disrupted.