Water acts as a solvent, temperature buffer and metabolite in the biological system. It provides a living environment for organisms, and acts as a medium of transport in biological processes.
Water is one of the most extraordinary molecules in life and one of the most fundamental requirements to biological processes. It covers 75 percent of the earth, and constitutes more than 80 percent of the human body. Water dissolves most of the compounds with ionic bonding including metal salts. Many molecular compounds also dissolve in water, such as sugars, small nucleic acids, amino acids and proteins. Water acts as a solvent for chemical reaction and facilitates the transport of dissolved compounds into and out of cells. It acts as a buffer to provide the right temperature for enzymes which catalyze most of the chemical reactions.
Water is a metabolite (chemical involved in a reaction) in virtually all reactions, either as a reactant or as the end result of reaction. For instance, water is required in such processes as photosynthesis, aerobic respiration and digestion. Water is a habitat for many organisms including fish.
Some of the important properties of water that support most of its functions include polarity, hydrogen bonding, cohesion and surface tension. These properties result from the combination of water molecules, and are essential for creation and support of life.