Friends and Neighbors—Interactions in a System: Phase Equilibria

  • Peter R. Bergethon


So far we have considered only homogeneous solutions. Such systems, while composed of a number of constituents, contain them in a single homogeneous phase. A phase is considered to be a state in which there is both chemical and physical uniformity. In a biological system, such a presumption is not realistic. Biological systems have many heterogeneous characteristics. Many of the processes in cells and living organisms involve the transfer of chemical species from one phase to another. For example, the movement of ions across a membrane such as the cell membrane or an intracellular organelle is often treated as transport between two phases, one inside and the other outside. The nature of the equilibria that can exist between phases will be the focus of this section. When different phases come into contact with each other, an interface between them occurs. This interface is a surface, and the properties of a surface are different from those of either of the phases responsible for creating it.


Phase Equilibrium Osmotic Pressure Free Energy Change Scatchard Plot Phase Rule 
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Further Reading


  1. Adamson, A. W. (1990) Physical Chemistry of Surfaces, 5th ed. John Wiley and Sons, Inc.Google Scholar
  2. Freeman G. R. (ed.) (1987) Kinetics of Non-Homoge- neous Processes. Wiley-Interscience, New York.Google Scholar
  3. Treptow R. S. (1993) Phase diagrams for aqueous systems. J. Chem. Ed., 60: 616–20.CrossRefGoogle Scholar
  4. Worley J. D. (1992) Capillary radius and surface tensions. J. Chem. Ed., 69: 678–80.CrossRefGoogle Scholar

Binding Interactions

  1. Attle A. D., and Raines R. T. (1995) Analysis of receptor-ligand interactions. J. Chem. Ed., 72:119–24. A nice review of the topic including the experimental tools used in biochemical laboratories.Google Scholar
  2. Parody-Morreale A., Câmara-Artigas A., and Sanchez-Ruiz J. M. (1990) Spectrophotometric determination of the binding constants of succinate and chloride to glutamic oxalacetic transaminase. J. Chem. Ed., 67: 988–90.CrossRefGoogle Scholar
  3. Monod J., Wyman J., and Changeux J. P. (1965) On the nature of allosteric transitions: A plausible model. J. Mol. Biol. 12: 88–114.PubMedCrossRefGoogle Scholar
  4. Koshland, D. L., Nemethy G., and Filmer D. (1966) Comparison of experimental binding data and theoretical models in proteins containing subunits. Biochemistry 5: 365–85.PubMedCrossRefGoogle Scholar
  5. Wyman J., and Gill S. J. (1990) Binding and Linkage. Functional Chemistry of Biological Macromolecules. University Science Books, Mill Valley, California.Google Scholar

Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • Peter R. Bergethon
    • 1
  1. 1.Department of BiochemistryBoston University School of MedicineBostonUSA

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