The plasma membrane is composed of lipoidal (fat-like) material in which proteins and protein complexes and whole functional systems are embedded... within specific regions known as lipid rafts (flat "islands" within the plasma membrane) or caveolae (cave-like structures within the plasma membrane). For example, the folate receptor (i.e., the cellular receptor for the B vitamin folic acid) is embedded in caveolae.

In the plasma membrane are incorporated such energy-dependent transport systems as Na + and K + transporting ATPase and amino acid transport systems. Besides the cell, membranes surround such systems as the endoplasmic reticulum, vacuoles, lysosomes, Golgi bodies, mitochondria, chloroplasts, and the nucleus, to mention just a few. The plasma membrane and membranes in general function in part as a permeability barrier to the free movement of substances between the inside and exterior of the cell or organelles that they surround.

CELL,  PROTEIN,  CECROPHINS (LYTIC PROTEINS),  MAGAININS,  MEMBRANES (OF A CELL),  GOLGI BODIES,  ENDOPLASMIC RETICULUM (ER),  LYSOSOMES,  TRANSMEMBRANE PROTEINS,  RECEPTORS,  LIPIDS,  LIPID BILAYER,  LIPID RAFTS,  CAVEOLAE,  MEMBRANE TRANSPORT,  TRANSLOCON,  ATPase,  AMINO ACID,  VITAMIN,  INTRINSIC PROTEIN,  PHOSPHATIDYL SERINE,  AQUAPORINS,  EFFLUX PUMP,  EFFECTORS (FUNGAL)