Dipal mitoylphosphatidylcholine is the major component of surfactant, or surface active agent
(an amphipathic molecule), that is secreted into lung alveoli to reduce the surface tension of the
primarily aqueous extracellular fluid of the alveolar epithelia. Alveoli, also referred to as
alveolar sacs, are the functional units of respiration. Oxygen and carbon dioxide diffuse across
the walls of alveolar sacs, which are one cell thick. The water on alveolar surfaces has a high
surface tension because of the attractive forces between the molecules. If the water’s surface
tension is not reduced, the alveolar sac tends to collapse, making breathing extremely difficult.
If premature infants lack sufficient surfactant, they are likely to die of suffocation. This
condition is called respiratory distress syndrome. Draw the structure of
dipalmitoylphosphatidylcholine. Considering the general structural features of phospholipids,
propose a reason why surfactant is effective in reducing surface tension.