Properties of Water
Life would not have existed on earth without water. Water molecules
are composed of one oxygen atom and two hydrogen atoms. Together, the
hydrogen and oxygen molecules form a shape that resembles the head of
While water molecules seem to be simple compounds, their properties
have profound impact on life. Because of the arrangement of hydrogen
and oxygen atoms, water molecules have polarized charges (one end is
positive and the other end is negative). Due to their polarized nature, 2
adjacent water molecules can form a linkage via a hydrogen bond.
The polarized nature of water causes other molecules to be either
hydrophilic (like water) or hydrophobic (afraid of water). This
property allows certain molecules to dissolve in water while preventing others from entering the cell. For example, hydrophobic
interaction can hold molecules together.
Another important property of water is its ability
to facilitate the transfer of molecules through osmosis. When 2
aqueous solutions are separated by a membrane that only allows the
passage of water molecules, water will move from the less concentrated
to the more concentrated side (Shown in the diagram below).
Hydrophobic interactions can hold molecules together: 2 or more
hydrophobic groups surrounded by water will tend to coalesce since
they thereby cause less disruption to the hydrogen-bonded structure of
water (Shown in the diagram below. Red hexagons represent hydrophobic
material and blue dots represent water molecules.).