Biomembrane lipids, diversity

Among the diverse components of biomembranes, lipids are essential in structural aspects. Lipids are defined operationally as derivatives of fatty acids and their metabolites. As lipids are usually amphiphilic molecules with hydrophobic hydrocarbon tails and hydrophilic head groups (as shown in Figure 1), the bilayer structures of biomembranes are held with hydrophobic forces to the tails and heads of lipids. Another major component of biomembranes is proteins. The weight proportion of proteins in biomembranes is often more than that of lipids. As proteins are more rigid than lipid assemblies, specific interactions by biomembranes are often related to proteins. Further, the sterols contained in biomembranes play unique roles in their apolar regions. As the functionality of biomembranes arises from the diversity of their composition, various kinds of molecules have been studied for biomembrane modeling. 

The composition of lipids varies markedly in a cell, and biomembranes and lipoproteins provide crisp examples about the diversity of different lipids. 

In view of the complexity and diversity of the functions performed by the various proteins embedded in a biomembrane (the integral proteins), it has been found convenient to incorporate single integral proteins or smaller lipophihc biomolecules into experimental models of biological membranes, so as to isolate and investigate their functions. This serves to reduce complex membrane processes to well-defined interactions between selected proteins, lipids, and hgands. There is... 

Another factor adds to an even more stunning complexity. This is due to the real structures of biomembranes. Built on the basic lipid bilayer, they insert a multitude of transmembrane proteins as well as diverse sugars with linear and branched structures into membrane that, in turn, can bind other proteins. Everybody who wishes to get a deeper insight into cell membranes should have a look at the Web site http //en.wikipedia.org7wild/Cell membrane. 

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