  Biological membranes mainly consist of lipids and proteins. While the
proteins have many functions as single molecules, the membrane as a whole
displays physical properties that cannot be explained on the single molecule
level. For example, membranes show melting events, phase behavior, and
elasticity. Biomembranes adapt their composition such that the physical
properties are maintained when the external conditions change. This gives a
role to changes in composition, to temperature and pressure. This article
introduces into the physics of membranes as a whole and shows how phenomena as
permeability, pulse propagation and the effect of anesthetics arise.
