Structure and Function of the Plasma Membrane

Abstract

The paucimolecular unit membrane model of the structure of the plasma membrane is critically reviewed in relation to current knowledge of the chemical and enzymatic composition of isolated plasma membranes, the properties of phospholipids, the chemistry of fixation for electron microscopy, the conformation of membrane proteins, the nature of the lipid-protein bonds in membranes, and possible mechanisms of transmembrane transport and membrane biosynthesis. It is concluded that the classical models, although not disproven, are not well supported by, and are difficult to reconcile with, the data now available. On the other hand, although a model based on lipoprotein subunits is, from a biochemical perspective, an attractive alternative, it too is far from proven. Many of the questions may be resolved by studies of membrane function and membrane biosynthesis rather than by a direct attack on membrane structure. My role today is to set the stage for the speakers to follow, who will discuss some recent developments in studies of the mechanisms of transport of solutes into cells. At the center of the problem of cellular transport lies the fact that there exists a selective barrier between the cytoplasm of the cell and the external environment through which a solute molecule can move often by the expenditure of cellular energy and by the mediation of a number of distinct components which together make up the particular transport system. This selective barrier to free diffusion is the plasma membrane. Now, it is apparent that although the kinetics of transport may depend on many other cell parameters, a complete understanding of the mechanisms of transport must include a description of the molecular composition and organization as well as the function of the plasma membrane. I shall present one man's assessment of where we now stand. THE PROBLEM IS POSED For many years cell biologists have been in general agreement that the problem of membrane structure was solved, at least to a first approximation,

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@inproceedings{Korn1968StructureAF, title={Structure and Function of the Plasma Membrane }, author={Edward D. Korn}, year={1968} }