Читать книгу Introduction to the Human Cell - Danton PhD O'Day - Страница 6

The most widely accepted model of the cell membrane is the “Fluid Mosaic Model” (Figure 2.1). By this concept the cell membrane consists of a continuous, double layer of phospholipids.

Figure 2.1. The fluid mosaic model of the cell membrane.

Proteins either are embedded in the bilayer or associated with either the cytoplasmic or extracellular face. Carbohydrates are linked to the proteins (glycoproteins) or lipids (glycolipids) only on the extracellular side. The phospholipid profiles of the cytoplasmic and extracellular layers differ. Cholesterol, in varying amounts depending on the cell type, lies within the membrane serving to stabilize it. In plants and bacteria, but not humans, the cell membrane is covered by a cell wall. In this chapter, our goals are to learn the major constituents of the biomembranes and to understand how they are organized into a functional cell membrane. The information is designed to set the stage for the chapters that follow.