The Biological Importance Of Water.

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Sanjayan Ravi        

The Biological Importance Of Water

In many ways, water is a miracle liquid. It is essential for all living things and is often referred to as a universal solvent because many substances dissolve in it. These unique properties result from the way in which water molecules interact with each other.

Water is a simple molecule made up of two hydrogen atoms and one oxygen atom (H2O). The atoms are bonded covalently via a shared pair of electrons. Thus there are four pairs of electrons orbiting the nucleus of the oxygen; two pairs are involved in the covalent bonds with hydrogen and two unshared pairs of electrons on the other side of the oxygen atom. Therefore oxygen develops a slight negative charge and the hydrogen atoms develop a slight positive charge making the molecules “polar”.

This slight charge means that when water molecules are close together, the positively charged hydrogen atoms are attracted towards the negatively charged oxygen atom of another water molecule, forming a weak hydrogen bond. The bonds are weak individually but the sheer number of them means that the total force keeping the molecules is considerable.

The partial charge that develops across the water molecule helps to make it an excellent solvent. Water dissolves many substances by surrounding charged particles and pulling them into solution. Salt (Sodium Chloride) is an ionic compound that contains alternating sodium and chlorine ions. When salt is added to water the partial charge on water molecules are attracted to Na+  and Cl-   ions. The water molecules work their way into the crystal structure and between the individual ions, surrounding them and dissolving the salt. The water molecule will line up differently according to which ions are being pulled into solution. The negative ends of oxygen molecules will surround the positive sodium and the positive ends of hydrogen will surround the chloride ions.

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Water can also separate covalently bonded molecules such as glucose and sucrose. The polar hydroxyl groups in it’s structure forms hydrogen bonds with the water separating the molecules from each other. Water’s property as a solvent is vital to life as most biochemical reactions such as respiration occur in solution. This is why cell cytoplasm contains about 90% water. Water can also dissolve toxic products in our body and take them out as sweat or urine. Water cannot dissolve non-polar substances such as fats and oils; these are used by organisms as cell membranes to separate cells and ...

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