AP BIOLOGY

Detailed explanation-1: -Surfactant is a macroaggregate molecule secreted by type 2 pneumocytes as the infant approaches term gestation. Surfactant is made up of 90% phospholipid and 10% proteins (surfactant protein [SP] A, B, C, and D). The primary function of surfactant is to reduce surface tension in the lung.

Detailed explanation-2: -Alveolar type II cells secrete a lipoprotein material called surfactant, whose primary function is to reduce the surface tension in the alveoli. Surfactant is a lipoprotein that consists mainly of dipalmitoylphosphatidylcholine and some glycoprotein components.

Detailed explanation-3: -Type II cells are spherical pneumocytes which comprise only 4% of the alveolar surface area, yet they constitute 60% of alveolar epithelial cells and 10-15% of all lung cells.

Detailed explanation-4: -walls are a group called granular pneumocytes (Type II cells), which secrete surfactant, a film of fatty substances believed to contribute to the lowering of alveolar surface tension.