How the Properties of Water are Related to Its Roles in Living Organisms and as a Living Environment for Living Organisms

How the Properties of Water are Related to Its Roles in Living Organisms and as a Living Environment for Living Organisms

Over 70% of the world’s surface is covered by water, 95% of which

consists of salty oceans; water is essential to all life forms. A

molecule of water consists of two hydrogen atoms covalently bound to

one atom of oxygen which gives a formula of H2O. When water molecules

are close together their positive and negative regions are attracted

to the oppositely charged regions of nearby molecules. The force of

attraction, shown in the diagram below as a dotted line, is called a

hydrogen bond. Each water molecule is hydrogen bonded to four others.

It is these hydrogen bonds and the polarity of water molecules which

are responsible for many of the unique characteristics and physical

properties of water. Firstly, the attraction created by hydrogen bonds

keeps water liquid over a wider range of temperature than is found for

any other molecule its size. Secondly, the energy required to break

multiple hydrogen bonds causes water to have a high heat of

vaporization; that is a large amount of energy is needed to convert

liquid water, where the molecules are attracted through their hydrogen

bonds, to water vapour, where they are not.

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Water bonds itself to other substances very easily which is why some

insects can glide on water. It also has a high surface tension which

means that it is adhesive and elastic. This means that it sticks to

the sides of vertical structures, for example it allows plants to move

water and dissolved nutrients from roots up to the leaves, and allows

the movement of blood through tiny vess...

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a positive end as a result of the polar covalent bonds within the

molecule) water is a solvent and readily interacts with other polar

and charged molecules such as acids, salts, sugars and various regions

of proteins and DNA. The water acts as a solvent for chemical

reactions and helps to transport dissolved compounds into and out of

cells. As a result of these interactions water can dissolve those

substances which are consequently described as hydrophilic (water

loving). In contrast, water does not interact well with non-polar

molecules such as fats, oil and water, and the large polymers (e.g.

polysaccharides and large proteins) do not mix. Non-polar molecules

are hydrophobic (water hating).

Overall, water is necessary for almost all life forms on Earth, and

without it almost nothing would be able to survive.