A Level Biology Practice Exam

What is the main function of lung surfactant?

1. To capture pathogens in the lungs

2. To coat alveoli and prevent them from collapsing

3. To transport oxygen in the bloodstream

4. To filter harmful gases from inhaled air

The correct answer is: To coat alveoli and prevent them from collapsing

The main function of lung surfactant is indeed to coat the alveoli and prevent them from collapsing. Surfactant is a lipoprotein complex that reduces surface tension at the air-liquid interface within the alveoli. This reduction in surface tension is crucial because it helps keep the alveoli stable during the breathing cycle, preventing their collapse (atelectasis) when the lungs deflate. By maintaining alveolar stability, surfactant enhances lung compliance, making it easier for the lungs to expand during inhalation. Additionally, a sufficient amount of surfactant is essential for proper gas exchange and efficient respiration; without it, individuals may experience respiratory distress.