title: Cellular Biophysics, Vol. 1: Transport
author:  Thomas Fischer Weiss 
description: Thomas F. Weiss is Thomas and Gerd Perkins Professor of Electrical and Bioelectrical Engineering, Department of Electrical Engineering and Computer Science, the Massachusetts Institute of Technology.
zlib_text: 19. The Cell Membrane: Transp ort and Permeability
  19. The Cell Membrane: Transport and Permeability
  I.  Characterization of Transport
  A.  Diffusion and Channels; the Aquaporins
  B.  Transporter Mediated Translocations
  II.  Molecular Mechanisms of Transport; The Glucose Transporters
  III.  Vectorial Enzymes
  IV.  Strategies for the Isolation of Transport Proteins 
  Suggested Reading 
  Web Resources
  References 
  Back to List of Chapters 
  The integrity of the cell depends on the presence of the plasma membrane. The membrane prevents the loss of internal components and metabolites. Its 
  ability to exclude some solutes and to permit the passage of others allows the maintenance of an internal environment that differs from the medium 
  external to the cell. The low concentration of Ca2+ in the cytoplasm permits its use as a sensitive signal for a variety of physiological regulatory effects. 
  Similarly, the creation of an Na+ electrochemical gradient provides a reservoir of energy that can be used f