The Properties of Water and It's Significance to Living Processes

Water typically forms 70 to 95% of the mass of a eukaryotic cell.

Although it is a simple molecule, water has the ideal properties to

support life.

A water molecule consists of one oxygen and two hydrogen atoms. Each

hydrogen atom shares electrons with the oxygen to form covalent bonds,

but the electrons are not shared equally. Oxygen has greater

electronegativity so has a greater pull on the electron causing the

electrons to move away slightly from the hydrogen atoms. Therefore the

water molecule has slightly positive and slightly negative regions,

which makes it a dipolar molecule

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Small positive charge ( +)

Small negative charge ( -)

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The small charges on water molecules cause attraction between them.

These forces of attraction are called hydrogen bonding, which gives

water its unique properties. The hydrogen bonding makes water

molecules difficult to separate. A greater amount of energy is needed

to break the hydrogen bonds to convert water into a gas than is needed

for similar compounds such as hydrogen sulphide (H2S).

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The fact that water is a dipolar molecule means that it is an

excellent solvent. It is often called the universal solvent since so

many things can dissolve in it. The water molecules will be attracted

to the substance molecules, will collect around it and will separate

it. Polar and ionic substances have and electrostatic charge so will

dissolve in water (they are hydrophilic). Non-polar substances, such

as fats, have no molecular charge so will not dissolve (they are

hydrophobic) which makes them ideal structural molecules in membranes

an...

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...It provides strength and

support as well as helping to form the shape.

Including photosynthesis, water also takes part in many chemical

reactions. It is a raw material for photosynthesis and it also takes

part in the digestion of substances such as proteins and lipids by

hydrolysis reactions.

Most organic substances in cells appear in their hydrated form. If the

water was to be removed, their chemical and physical properties would

be affected.

Water is essential to life for many reasons, some of which have been

discussed. Sometimes, however, there is an advantage to living tissue

to become dehydrated. Dehydration in reproductive structures such as

pollen and seeds ensures that they can survive periods of water

scarcity.

Overall water plays a very significant role in life processes in most

organisms.