Lamellar bodies in type II pneumocytes primarily store which surfactant component?

• A. DPPC
• B. Collagen
• C. Hemoglobin
• D. Cholesterol

Answer: (A)

Lamellar bodies in type II pneumocytes are specialized storage and secretory organelles for pulmonary surfactant. The surfactant they hold is rich in lipids, with the dominant component being dipalmitoylphosphatidylcholine (DPPC), a disaturated phospholipid that makes up the majority of the surfactant lipid and is essential for lowering surface tension at the air–liquid interface in the alveoli. When these lamellar bodies fuse with the plasma membrane, surfactant is released onto the alveolar surface where DPPC helps form a stable film, preventing alveolar collapse during breathing. While surfactant also contains specific proteins (SP-A, SP-B, SP-C, SP-D), DPPC is the key lipid component stored in these organelles. Other substances listed, like collagen, hemoglobin, or cholesterol, are not the primary stored components of lamellar bodies in this context.