Cellular membranes, specific recognition functions

Membranes play essential roies in the functions of both prokaryotic and eukaryotic cells. There is no unicellular or multicellular form of life that does not depend on one or more functional membranes. A number of viruses, the enveloped viruses, also have membranes. Cellular membranes are either known or suspected to be involved in numerous cellular functions, including the maintenance of permeability barriers, transmembrane potentials, active as well as specific passive transport across the membranes, hornione-receptor and transmitter-receptor responses, mitogenesis, and cell-cell recognition. The amount of descriptive material that might be included under the title of biological membranes is encyclopedic. The amount of material that relates or seeks to relate structure and function is less, but still large. For introductory references see Refs. 53, 38, 12, 47, 34, 13. Any survey of this field in the space and time available here is clearly out of the question. For the purposes of the present paper we have selected a rather narrow, specific topic, namely, the lateral diffusion of molecules in the plane of biological mem-branes.38,12,43,34 We consider this topic from the points of view of physical chemistry and immunochemistry. 

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