The Biological Importance of Water In Living Organisms
Water is the most important molecule in cells, the whole organisms and on earth, this is due to it’s unique physical and chemical properties. ” A water molecule, because of its shape, is a polar molecule. That is, it has one side that is positively charged and one side that is negatively charged”(1). A water molecule is made up of two hydrogen atoms and one oxygen atom and the bonds between these atoms are single covalent bonds. Fig 1. The polarity of a water molecule (2)
In a water molecule two hydrogen atoms form single polar covalent bonds with an oxygen atom. “Oxygen is more electronegative (6 valence electrons) - region around oxygen has partial negative charge. Hydrogen is less electronegative (1 valence electron) -region near the two hydrogen atoms has a partial positive charge.” (3) A water molecule is a polar molecule with opposite ends of the molecule with opposite charges. Fig.2. Positively and Negatively charged ions in water.
“Many water soluble materials which, when dissolved in water, split apart into electrically charged atoms or groups of atoms called ions. The ions with the negative charge are called anions and those with the positive charge are cations.” (7) Water is vital to living organisms because between 60 to 70% of our body is made up of water. One of the main functions of water in living organism is its use as a solvent, because water is slightly ionised, other polar molecules such as salts, sugars and amino acids dissolve readily in water. This will allow water to be used for the transportation of many substances, for example in the bloodstream of animals and the xylem and phloem vessels found in plants. Fig.3. The dipolar bonding in water (8)
The dipolar bonds between water molecules show a large amount of energy and this determines the temperature of the water.
Water can also be used in this way to transport...
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