Florida State Paramedic Practice Exam

How does gas exchange occur in the body?

1. Active transport

2. Diffusion

3. Osmosis

4. Filtration

The correct answer is: Diffusion

Gas exchange in the body primarily occurs through the process of diffusion. This is a passive transport mechanism where molecules move from an area of higher concentration to an area of lower concentration until there is an equal concentration on both sides. In the context of the respiratory system, oxygen diffuses from the alveoli in the lungs, where its concentration is high, into the blood in the surrounding capillaries, where its concentration is lower. Conversely, carbon dioxide diffuses from the blood, where its concentration is higher, into the alveoli to be exhaled, where the concentration is lower. Diffusion is crucial because it does not require energy; instead, it relies on the natural kinetic movement of molecules. This process effectively allows for the exchange of gases in the lungs and at the cellular level throughout the body, enabling essential physiological functions such as cellular respiration and maintaining proper pH balance. Understanding diffusion is fundamental for grasping how oxygen delivery and carbon dioxide removal occur in the human body.