Importance of water | Role Of Water |

Importance of water.

Water is a medium of life. It is the most abundant compound in all organisms. Different organisms contain 65 to 89 % of water. A bone cell of human contains 20 % and a brain cell contains 85 % water. Water shows following properties:

1.  Role of water in chemical reactions.

All the reactions take place in the presence of water. It takes part in many biochemical reactions.

For example, water causes hydrolysis of macro molecules. Water is also used in photosynthesis.

2. Solvent properties.

Water is a polar or ionic molecule. So it is an excellent solvent for polar substances.Ionic substances dissolve in water and dissociate into positive and negative ions. Ionic compounds have charged groups in their molecules. So they disperse in water. lons and molecules move randomly in solution. Therefore, they can react easily with other molecules and ions. Due to this property, all reactions occur in water medium in the cells in the presence of enzymes. These enzymes act only in aqueous environment. Non-polar molecules like fats are insoluble in water. So these compounds form membranes of cells.

 3. Heat capacity

The. number of calories required to raise the temperature of 1g of water from 15 to 16° C is called specific heat capacity of water. The specific heat capacity of water is 1.0./Water has a great ability to absorb heat without much change of its own temperature. So water acts as temperature stabilizer for the organisms in the environment.  It protects the living material against sudden thermal  changes. 

4. Heat of vaporization

The amount of heat required to change 1 gm of water into vapours is called heat of vaporization or specific heat of vaporization. It is expressed in calories per grams. The specific heat of vaporization of water is 574 Kcal/Kg. So water absorbs much heat when changes from liquid to gas. Thus water regulates heat produced during oxidation. It also cools the plants during transpiration. It cools the animals during evaporation of water. The eveporation of only 2 ml of water from a litre of water lowers the temperature of remaining 998 ml water by 1°C.

5. Ionization of water

The water molecule ionizes to from H⁺ and OH⁻ ions.

            H2O  ⇿ H⁺ + OH⁻.

This reaction is reversible. But equilibrium is maintained the concentration  of H" and OH ions is about 10' mole/litre in pure water at 25° C. The H' and OH ions affect and take part in many reactions in cell.

6. Protection

Water is a lubricant . It reduces friction. Thus it protects the body parts from damage. Example, tears protect the eye from the rubbing by eyelids. Water forms a protective layer of fluid around the organs and protects them from trauma.