| Popis: |
This chapter focuses on the most abundant molecule in all living systems. Without it enzymes do not function normally, DNA collapses into a tangled mess, and no dielectric continuum (solvent) exists, within which so many physiological processes take place. After brief discussion of pure water we focus here upon the cellular and molecular aspects; however it is quite evident that water participates at all levels of biological organization, from molecular to biosphere. We concentrate on the aqueous phase properties of cells and consider only briefly the importance of the primary hydration of intracellular solutes, a well studied and non-controversial issue. Most thought about cell biology has been built on the assumption that the structure and properties of intracellular water are not significantly different from those of pure water (or that in ordinary dilute aqueous solutions). That widely held assumption appears to be questionable in view of a large body of evidence to the contrary. Attention is paid to the large amount of data showing that the water adjacent to surfaces exhibits interesting and unusual physical properties compared to the ordinary bulk liquid. We make the case that the internal environment of cells is characterized by an enormous surface to volume ratio and argue that, on this basis alone, we should expect the water in cells to deviate in its properties. A number of examples are summarized which indicate that this expectation has been documented experimentally, but has thus far not been accommodated within popular prevailing paradigms. We consider some examples of the importance of these interesting properties of intracellular water to cell structure and function. |
