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The biological importance of water

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The Biological Importance of Water Water is argued to be the most important molecule. It is essential to life itself and without it life on earth would not exist. It is a major component of cells making up between 70% and 95% of the mass of a cell. Humans are made from approximately 70% water whereas soft-bodied creatures such as jellyfish are made up by 96% water by mass. As well as forming organisms it also provides an environment for them to live in as 75% of the earth is covered by water. Water is one of the simplest linear molecules made up of two hydrogen atoms and one oxygen atom. Its chemical formula is H2O and the atoms are joined by covalent bonds. These are formed when electrons in the outer shell are shared, however in water's case there are a large number of protons in the oxygen nucleus, which have a strong attraction to the shared electrons. This attraction is stronger than the one from the tiny hydrogen nuclei. ...read more.


This is why cell cytoplasm contains about 90% water. Because water cannot dissolve hydrophobic substances such as fats and oils, it makes them good at waterproofing organisms and as cell membranes. The thermal properties of water are also interesting because they are unlike other molecules. Water has a boiling point of 100?c and a melting point of 0?c. This is unusual for a molecule of its size as other molecules with similar properties are all gaseous at room temperature whereas water is a liquid. It is the hydrogen bonds that hold water molecules in a liquid store. It takes a lot of heat energy to be able to raise the temperature of water significantly, but once warm it cools slowly. This is an advantage to creatures where a constant body temperature has to be maintained. This constant temperature with very little change will remain in large amounts of water. A large amount of bonds holding water molecules together requires a considerable amount of energy to separate the bonds and turn the liquid to favour. ...read more.


Also water is transparent allowing aquatic plants to photosynthesis and other organisms to live. The hydrogen bonds between the molecules make water highly cohesive. Water is formed into spherical droplets which have the maximum inner area and least surface area when in contact with a hydrophobic material. It 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. Water is incompressible due to strong hydrostatic forces. As a result of this soft-bodied creatures such as worm and jellyfish do not require a skeletal system for support. Water allows cells filled with water to become turgid and due to its incompressibility plants can support themselves. In conclusion water's unique properties make it perhaps the most biologically important substance on the planet. No other substance shares similar properties to water and in the way that one single molecule can possess such varied and essential characteristics. ...read more.

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