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The Biological Importance Of Water.

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Introduction

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. ...read more.

Middle

The ability of water molecules to stick together allows a plant to transport water to leaves in the highest parts of the tree. Water also has various thermal properties as a temperature stabiliser. Water has a boiling point of 100�C and a melting point of 0�C, this is unusual for a molecule of it's size (Water has a RMM of 18) because other molecules of similar size such as: ammonia, NH4 with RMM the same as water and Carbon dioxide with RMM of 44, are all gases at room temperature whereas water is a liquid at room temperature. This because of the hydrogen bonds which holds the molecules together. The hydrogen bond also lets the water to have a high specific heat capacity. A high amount of energy is needed to heat water. Once water is warm it cools very quickly, this is fundamental to life where internal body temperature has to be maintained at a constant temperature and fluctuations can result in breakdown of vital processes. Large bodies of water will remain at a constant temperature allowing temperature regulations for organisms far more straightforward. ...read more.

Conclusion

Water molecules are highly cohesive because of the hydrogen bonds between the molecules. Water forms spherical droplets, which have the maximum inner area and least surface area when in contact with a hydrophobic material. The cohesive properties of water allows plants to pull up water through xylem vessels from the roots to the leaves, this is called the transpiration stream. It also means that the water molecules where the water meets the air will be tightly held together and the water molecules below them to form an elastic film known as surface tension. Small creatures can get stuck in the surface water because they cannot break the water surface tension, creatures like water skaters can move across the surface of the water without sinking as they have hydrophobic feet which stops them from breaking the surface tension. As water has strong hydrostatic, water is incompressible. This provides support for soft-bodied creatures such as worms, slugs and jellyfish, which therefore do not require a supporting skeletal system. Water allows cells filled with water to become turgid and due to its incompressibility plants can support themselves. Sanjayan Ravi 1 ...read more.

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