The plasma membrane is primarily composed of phospholipids, which form a bilayer structure essential for membrane fluidity and selective permeability. This bilayer creates a hydrophobic barrier that regulates the entry and exit of substances, crucial for maintaining cellular homeostasis. Phospholipids provide the fundamental framework upon which proteins, cholesterol, and glycoproteins are integrated to assist specific functions like signaling and transport. In surgery, understanding this composition is vital for targeting membrane integrity and drug delivery systems. Disruption of the phospholipid bilayer can compromise cell viability and impact tissue repair.

Reference: Molecular Biology of the Cell, Alberts et al., 6th Edition.