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An overview is given of the fundamental physics underlying the self-assembly, molecular organisation and electrical properties of the membranes that envelop living cells. These ultra thin (∼ 6 nm) membranes act as a diffusion barrier between the cell interior (cytoplasm) and the external medium. They consist basically of a bi-molecular film of lipid molecules in which are embedded functional proteins that perform a variety of functions, including energy transduction, signalling, transport of ions (and othermolecules), etc. Some examples are also presented of the fascinating and socially and commercially important applications of membrane biophysics.

The optimum conditions to allow proliferation of cells for the secretion of some growth factors and cytokines and the proliferation of cells in different media that do not contain proteins or serum from animals (serum-free media) were investigated. The culture of cell lines for the commercial production of products involves optimisation of cell proliferation and secretion in media from which the requisite proteins can be economically extracted. Some of these problems were addressed in this study. We used two different clones from a human myeloma cell line for adaptation to serum free medium in order to characterize long-term effects of the new medium. We gradually decreased serum content of medium and the results showed that cell mortality increased with serum reduction, antibody production lost by survived clones, and secretion of cytokines were always retained.