The Plasma Membrane


Membrane Functions
  • Form specialized compartments by selective permeability
    • Unique environment
    • Creation of concentration gradients
    • pH and charge (electrical, ionic) differences
  • Asymmetric protein distribution
  • Cell-Cell recognition
  • Site for receptor molecule biding for cell signaling
    • Receptor binds ligand (such as a hormone)
    • Induces intracellular reactions
  • Controls and regulates reaction sequences
    • Product of one enzyme is the substrate for the next enzyme
    • Can "line up" the enzymes in the proper sequence

Membrane Structure According to the Davson-Danielli Model

Membrane Structure According to the Fluid Mosaic Model of Singer and Nicolson


Membrane Lipids

Bilayer Formation

Membrane Fluidity

How Cells Regulate Membrane Fluidity

Membrane Carbohydrates

Membrane Proteins


An Example - Asymetry of Intestinal Epithelial Cell Membranes