AP BIOLOGY

Detailed explanation-1: -It is established that pulmonary surfactant reduces surface tension at the air–water interface in the alveoli, thereby preventing collapse of these structures at end-expiration. In this manner, surfactant reduces the work associated with breathing.

Detailed explanation-2: -By adsorbing to the air-water interface of alveoli, with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.

Detailed explanation-3: -The cohesive forces between the water molecules are very strong making the surface tension of water high. As surfactants absorb they break these interactions. The intermolecular forces between surfactant and water molecule are much lower than between two water molecules and thus surface tension will decrease.

Detailed explanation-4: -Introduction. Pulmonary surfactant reduces the surface tension at the air-liquid interface throughout the lung by forming a lining layer between the aqueous airway liquid and the inspired air. The major component of surfactant, dipalmitoyl-phosphatidylcholine (DPPC), is an amphiphatic phospholipid.

Detailed explanation-5: -The surfactant lines the alveolar walls over the water film, and then reduces the surface tension and thus the collapsing pressure.