AEMCA Practice Exam

Which of the following best describes the action of cyanide in the body?

1. It enhances respiration in cells

2. It inhibits the ability of cells to utilize oxygen

3. It promotes increased oxygen absorption

4. It acts as a muscle relaxant

The correct answer is: It inhibits the ability of cells to utilize oxygen

Cyanide is a potent poison that interferes with the body's ability to use oxygen at the cellular level. Specifically, it inhibits the action of cytochrome c oxidase, a crucial enzyme in the electron transport chain within mitochondria. This enzyme is essential for cellular respiration, as it helps facilitate the transfer of electrons to oxygen, thereby enabling the production of adenosine triphosphate (ATP), the energy currency of the cell. When cyanide binds to this enzyme, it effectively prevents cells from utilizing oxygen, despite the presence of adequate oxygen in the blood. As a result, cells cannot produce energy efficiently, leading to cellular death and, ultimately, systemic failure. The incorrect options involve misunderstandings about the role of cyanide. For example, it does not enhance respiration—rather, it disrupts that process. It also does not promote increased oxygen absorption; instead, it blocks the use of oxygen that is available. Lastly, cyanide is not known for any muscle relaxant properties; its lethal effects stem primarily from its ability to disrupt oxygen utilization in cells.