In an influential review in the early 1970s, Singer and Nicolson summarized the available information on the property of the lipid bilayer, and proposed a "fluid mosaic" model of the plasma membrane . These authors suggested that biological membranes are two-dimensional fluids of lipids, in which integral membrane proteins are dissolved; peripheral proteins are attached to the surface of the membrane and protein milieu (Fig. 3.1). Lipids and proteins were proposed to have unrestricted lateral mobility, but restricted transverse mobility. These considerations were construed to result in a homogeneous distribution of lipids and proteins in biological membranes. However, the spatial and temporal inhomoge-neity of lipids, while not explicitly advocated, was certainly not ruled out. In fact, domain models of cell membranes, as mosaic rather than fluid, have existed for a long time, based primarily on the properties of lipids in artificial liposome membranes [2,3]. The fluid-mosaic model of Singer and Nicolson also considered the possibility of small membrane domains in the fluid cell membrane bilayer. However, all these models of cell membranes did not focus on relating any specific biological functions that required domain formation.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.