The Role Of Water In Living Organisms

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Water has a great number of roles in living organisms, this is largely

to do with the structure and covalent bonding in a single water

molecule, and between water molecules. Around 75% of the earth is

covered in water, and it is reffered to as the most important

Biochemical.

Its chemical symbol is: H2O

In a water molecule there are two bonding pairs and two non-bonding

pairs of electrons. These four pairs of electrons repel one another,

forming a tetrahedral pattern. Because they repel they are as far from

each other as possible.

The two electrons in each of the oxygen-hydrogen bond are not shared

equally. They are more strongly attracted to the oxygen. The bond is

polar, it has a 'negative part' (the oxygen) and a 'positive part'

(the hydrogen).The hydrogen bond is very weak, about ten times weaker

than a single covalent bond.

Water has importance inside cells and outside. This may be because of

its chemical and physical properties; it can be found naturally in all

three of its states. At room temperature water is in a liquid state,

It boils at 100ºC and freezes at 0ºC.

However its molecules are bonded together by hydrogen bonds, this

raises it's melting and boiling points, e.g. its boiling point would

be -120ºC rather than 100ºC.

Water can also be used as a solvent because of it polarity. Many

things will dissolve in it, and more reactions take place while in

solution with water. Often in organisms substances must be in solution

and water is the solvent.

Plants can only obtain mineral salts in solution so require water to

live. Also human digestion will only dissolve soluble foods, meaning

large starch molecules must be broken down into soluble sugars. Also

many organisms living in water spend most of their lives underwater,

yet they require oxygen to live and respire, and as water is such a

good solvent the required oxygen gas is dissolved in the water and the

organisms can use it.

Water is the most abundant component in any organism, proving its

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