Over two thirds of the Earth today is water, and living organisms are 80% water by mass, they must retain this to survive. Water is a vital solvent and reactant in everyday life.

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The structure and function of water in living organisms

        Over two thirds of the Earth today is water, and living organisms are 80% water by mass, they must retain this to survive.  Water is a vital solvent and reactant in everyday life.  

The formula for water is H20.  Compared to other molecules H20 is very small.  Two hydrogen atoms are covalently bonded to one oxygen atom.  Covalent bonds are formed by sharing electrons in outer energy levels of atoms.  The large number of protons in the oxygen nucleus has a stronger attraction for shared electrons than the hydrogen nucleus.  Oxygen therefore pulls electrons slightly closer to itself so that it develops a weak negative charge represented as ς- and hydrogen develops a slight positive charge represented as ς+.  This means the charge distribution is unequal and it becomes a polar molecule.   Adjacent molecules of water are attracted because the negatively charges O attracts a positively charged H.  The bonds between the molecules are called hydrogen bonds and they make water very stable.

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Water has many functions which are essential for its uses.  It has a high specific heat capacity; this means that it takes a lot of heat to break the hydrogen bonds and for water to evaporate into a gaseous form.  A lot of heat energy is needed to evaporate water from the surface of the skin.  Having a high specific heat capacity enables water to act as a buffer.  This means that it’s essential in endothermic organisms that need to maintain a constant body

Temperature in ...

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