What effect does cyanide have on the body?

Cyanide is a potent poison that primarily affects the body's ability to use oxygen at the cellular level. More specifically, it inhibits cellular respiration by binding to cytochrome c oxidase, a critical enzyme in the electron transport chain within mitochondria. This enzyme plays a fundamental role in the process of aerobic respiration, where cells convert oxygen and glucose into ATP, the energy currency of the cell. When cyanide binds to this enzyme, it effectively prevents cells from utilizing oxygen, leading to a state of cellular hypoxia despite the presence of oxygen in the tissues. This disruption in cellular respiration can cause a cascade of harmful effects throughout the body, resulting in symptoms such as dizziness, headaches, and potentially fatal outcomes if exposure is significant. This understanding clarifies why the correct answer highlights the inhibition of cellular respiration as the primary effect of cyanide on the body.