Lipids in Aqueous Solution: The Formation of the Cell Membrane
Thus far, we have explored the properties of inorganic aqueous solutions and bulk water. Yet cells and biological systems are not composed of simple, homogeneous solutions or bulk aqueous phases. The organization of biological systems, and certainly eukaryotic cells, depends on compartmentalization of cellular functions. We will explore this important topic in the following chapter. This compartmentalization, which allows varied microenvironments to exist in proximity, is dependent on the membranes that constitute the boundaries of the compartmentalized organelles. Virtually all biological membranes are composed of lipid molecules arranged in bilayers, with inserted or attached protein and carbohydrate molecules playing a variety of roles at or in the lipid phases. Although membranes in cells are made up primarily of hydrophobic lipid elements, they almost always separate into two phases whose predominant species is water. The arrangement of these aqueous-lipidaqueous “phases” leads to a generalized mechanism through which the cell can perform a wide variety of tasks that allow it to sense, judge, and respond to its environment. How can we understand membrane formation? We start by exploring the interactions of water with nonpolar molecules and then focus on certain biophysical and biochemical aspects of lipid membrane formation, from which a more complete description of the cell can eventually emerge.
KeywordsElectron Paramagnetic Resonance Lipid Molecule Aliphatic Chain Critical Micelle Concen Polar Head Group
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- Israelachvili J. (1992) Intermolecular and Surface Forces, 2d. ed. Academic Press, London.Google Scholar
- Kotyk A., Janacek K., and Koryta J. (1988) Biophysical Chemistry of Membrane Functions. John Wiley and Sons, New York.Google Scholar
- Small D. M. (ed.) (1986) “The Physical Chemistry of Lipids.” In Handbook of Lipid Research, vol. 4. Plenum Press, New York.Google Scholar
- More details on aqueous clathrate structure can be found in the series edited by Franks (see listing under chapter 20) Articles on clathrate organization around biomoleculesGoogle Scholar
- Byrn M. P., Curtis C. J., Hsiou Y., Khan S. I., Sawin P. A., Tendick S. K., Terzis A., and Strouse C. E. (1993) Porphyrin sponges: Conservation of host structure in over 200 porphyrin-based lattice clathrates, J. Am. Chem. Soc., 115:9480–97. This article discusses the application of the clathrate ideas to a nonaqueous, highly structured “solvent,” tetraarylporphyrin molecules!Google Scholar
- Teeter M. M. (1992) Order and disorder in water structure of crystalline proteins. Dev. Biol. Stand., 74: 6372.Google Scholar
- Schindler H. (1989) Planar lipid-protein membranes: Strategies of formation and of detecting dependencies of ion transport functions on membrane conditions. Methods in Enzymol., 171:225–53. Oriented to laboratory work. A relatively recent review of the field of artificial membranes.Google Scholar