Transport Across Membranes

Cell membranes control the movement of substances into and out of cells. The fluid mosaic model describes the plasma membrane as a dynamic structure composed of a phospholipid bilayer with embedded and peripheral proteins, cholesterol, and glycoproteins. Understanding membrane structure, the mechanisms of transport, the factors that affect membrane permeability, and the basics of cell signalling is essential for A-Level Biology.

Key Definition: The fluid mosaic model (proposed by Singer and Nicolson, 1972) describes the cell membrane as a phospholipid bilayer with a mosaic of proteins that can move laterally within it.

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The Fluid Mosaic Model