Water

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Water ( Molecular formula:H2O) constitutes of two hydrogen atoms and a single oxygen atom. The hydrogen atoms are linked to the oxygen atoms by covalent bonds Since Oxygen has a much higher Electronegativity than Hydrogen, the distrubution of electrons is more dense towards the Oxygen molecule thus creating a slightly negative reigion.. When water molecules interact with each other, the positively charged region (hydrogen atom) of one water molecule forms a weak hydrogen bond with the negatively charged region (oxygen atom) of a second water molecule [1].  This is a hydrogen bond and although it isn't as strong as a covalent bond, it is highly stable and is responsible for the properties and thus abundance of water on Earth.

Water is a bent molecule there the distribution of charge is assymetric. As a result of the charged regions in water, water is a polar molecule and can conduct electricity. Water molecules react with molecules in aqueous solution through the formation of hydrogen bonds and via ionic interactions. These interactions mean that water is a good  and can dissolve polar molecules and ions. Water has small molecules and maintains its physical state of bein a liquid over a large range of temperatures.It is also highly cohesive. Networks of hydrogen bonds hold the structure of ice and liquid water together. These interactions are responsible for the cohesion of water. Water is involved in many different reactions and can affect several noncovalent bonds with its presence. Examples of noncovalent bonds that the presence of water can affect are electrostatic interactions, hydrogen bonds and van der Waals interactions. Furthermore when water cannot react with nonpolar molecules through hydrogen bonding or ionic interactions, the result is the hydrophobic effect that is accompanied by hydrophobic interactions.[2]

Humans contain around 40 litres of water and both unicellular organisms and multicellular cells live in water.

Many diseases are associated with water, for example excess water (hyperhydration), not enough water (dehydration) and many microorganisms use water as a form of transport and spread through water, e.g. Cholera.


References:

  1. Alberts et al., Molecular Biology Of the cell, 5th edition, 2008, Garland Science, New York, pg 51
  2. Berg Jeremy M., Tymoczko John L., Stryer Lubert., (2007) Biochemistry, Sixth Edition, New York, W.H. Freeman and Company. P8-9

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