The Biological Importance of Water B io F actsheet September 1998 Number 30 1 Water is a polar molecule i.e. it has both positively charged and negatively charged areas. Water is made up of two positively charged hydrogen atoms and one negatively charged oxygen atom (Fig 1). Water (H2O) is the most abundant molecule in cells, whole organisms and on earth. This is a consequence of the unique physical and chemical properties of water. This Factsheet will briefly explain the significance of these physical and chemical properties, then discuss the primary roles of water in animals and plants. As a result of this polarity (the uneven distribution of charges), adjacent water molecules are attracted to and become bonded to each other. The