(diagram)
Capillary action, cohesive/ adhesive properties
The effects of very large numbers of hydrogen bonds are responsible for many of the properties of water. Water molecules tend to cling to each other and to other polar molecules. Attraction between water molecules is referred to as cohesion; attraction between water molecules and other polar molecules is referred to as adhesion. Water also occurs as moisture in the upper portion of the soil profile, in which it is held by capillary action to the particles of soil. The cohesive property in water molecules is very important in transporting materials in solution within organisms. E.g. Transport of ions in solution in the xylem of plants and in the transport of the soluble products of digestion in the blood plasma of animals.
Solvent properties
Water is the major chemical constituent in cells, of all living matter. From 60 to 95% of the weight of living organisms is water. Water acts as a solvent, transporting, combining, and chemically breaking down the substances including fats, carbohydrates, proteins, salts, and similar chemicals in living cells. Blood in animals and sap in plants consist largely of water and serve to transport food and remove waste material. Water is a solvent when it is mixed with salts (sodium chloride), when salts dissolve, it breaks down into its constituents, sodium and chlorine ions. They form hydrogen bonds with water molecules and each ion becomes surrounded by a cloud of water molecules (hydration shell) Water molecules can form hydration shell around any molecule which has an electrical charge.
Osmosis
Biological membranes are permeable to water, but there is no net movement of water into and out of cells in less osmosis occurs. Osmosis is the diffusion of water molecules from a high concentrated area to a low concentrated area, through a partially permeable membrane. E.g. Osmometer experiment.
Support role
Metabolic role
Water also plays a key role in the metabolic breakdown of such essential molecules as proteins and carbohydrates. This process called the hydrolysis goes on continually in living cells.
Others
Water has a high specific heat capacity, meaning that it requires a lot of energy to raise the temperature of 1kg by 1degree. So it can maintains relatively constant temp. in a long period of time. This is important to sea creatures, because sudden temp. changes in their environment are avoided.
Insulation: max density at 4 degree. As the temp of a pool of water falls and the water on the surface freezes and form ice. It insulates the water below, keeping aquatic organisms to live and this is especially important in cold climates and places with cold seasons.