It is impossible to envisage any form of life without a fl uidenvironment.
Water, functioning as a solvent, is responsible for the movement of
nutrients to cells and for the movement of metabolic end products from
the cells for removal via the kidneys, lungs, and gut. Water also moves
hormones and other chemical signals within and among cells, tissues, and
organs. The capability of water to serve as such a successful solvent lies
in its dipolar structure. For example, salt is readily dissolved in water. This
is due to the large dielectric constant of water; thus, molecules linked by
ionic bonds will dissociate in water and not in other solvents that have a
different chemical structure.