Explain the role that water plays in living systems.

ANSWER: Water is a poor solvent for nonpolar substances. Thus, through hydrophobic interactions, lipids coalesce, membranes form, boundaries are created delimiting compartments, and the cellular nature of life is established. Because of its very high dielectric constant, water is a medium for ionization. Ions enrich the living environment in that they enhance the variety of chemical species and introduce an important class of chemical reactions. They provide electrical properties to solutions and therefore to organisms. The thermal properties of water allow effective temperature regulation in living organisms. The heat generated within an organism as a result of metabolism can be efficiently eliminated through evaporation or conduction of water.