ABSTRACT
Lipid bilayers are among the most important ‘construction materials’ for the cell (Alberts et al. 2002). A bilayer membrane constitutes a exible barrier that separates the interior and exterior of a cell, encapsulates the nucleus and can perform a number of roles such as acting as a functional host for protein production. Membranes appear in at (plasma membrane), spherical (vesicular transport), tubular (transport) or tortuous and possibly bicontinuous (Endoplasmic Reticulum, ER and Golgi apparatus) forms in the cell, depending on function and composition. Lipid membranes comprise a vast variety of lipids and other constituents, of which cholesterol is a prime player, whose composition determines the large-scale properties necessary for the function of the particular membrane. Such properties include exibility, stiffness with respect to bending and stretching, viscosity and uidity, overall shape and degree of internal order. Most biological membranes contain a large area fraction, up to 30% or more in some cases, of membrane proteins, which themselves inuence membrane properties and whose specic functions act in concert with the local lipid compositions to direct their biological role. The subjects of membrane elasticity and dynamics, membrane-protein interactions and membrane-lament interactions are vast and of vital importance to a concrete biophysical understanding of cell processes.
