The Role of Water in Living Organisms

The Role of Water in Living Organisms
The Role of Water in Living Organisms Water is one of the most abundant substances on the planet. It can be found naturally in all three states; solid (ice), liquid (water), and gas (steam). However, chemically it is very unusual. For example, water molecules are slightly polar i.e. they have a positive and negative end. Due to this difference in electro-negativity the slightly positive charge on the hydrogen atom is attracted to the slightly negative charge on the oxygen atom in another molecule. This bond is called a hydrogen bond and is what causes the water to have its unusual properties. For example, other molecules of the same size of water (H2O) are all gases at room temperature and pressure (R.T.P). Without the hydrogen bonds, water too would be a gas at rtp and would have a boiling point of -120?C. Because it is polar, water also has uses as a solvent.
Other polar substance are dissolved by water as the electrostatic attractions between the water molecules and the ions are greater that the attraction between the anion and cation. The water molecules surround the ions and thus the ions become hydrated. Polar substances that dissolve in water are said to be hydrophilic or ?water-loving?. The ability of water to be a solvent has uses in organisms. For reactions within the body to take place, they usually have to be in solution. Therefore, using water as the solvent enables more reactions to take place as more compounds may be dissolved. It is not only human that use water as a solvent, plants are only able to take up mineral salts in solution and so use water. Also, organisms that live in marine environments still need oxygen to respire. The only reason they survive is because oxygen is dissolved in the water. This would not be possible if the water molecule was non-polar. As I have said, water is the most abundant molecule on the planet, but is also the most abundant molecule organisms. The lowest percentage composition is 20% in seeds, with the highest being 99% in jelly fish. Water plays a vital role in metabolism in all cells and photosynthesis in plants. All cells, whether plant of animal, water is used for hydrolysis (the breakdown of a substance by water). For example, the break down of polysaccharides to monosaccharides forming a glycosidic bond, which is used as a medium for chemical reactions. Water also has an important role to play in osmosis as for gaseous exchange to take place, a moist environment is needed. On a much larger scale it is used for transport. The blood is mostly water, and is used to transport food, hormones, waste products and oxygen. Similarly in plants sap, which contains water, is used to transport food and other substances to the cells. Another use for water is lubrication. The synovial fluid around joints it composed mostly of water. Water surrounds many of the internal organs to provide protection and lubrication. Examples would be pleural fluid around the lungs, and the amniotic fluid that protects a foetus in the womb. Yet another use of water is for support. In plants, the cells have sap vacuoles which fill which water, due to osmosis, and cause the cell to become turgid (stiff) supporting the leaves and stem of the plant. The common earthworm uses the supporting characteristics of water, as it has a hydrostatic skeleton. Water can also be used as a habitat. Life is thought to have originated in an aqueous environment, and it still provides for a variety of life today. There are many reasons for such diversity of life. The water around living cells can act as a protective shield, preventing cells from drying out, as they would on land; it provides support and buoyancy so hard tissue and bones are not required in such large amounts; the temperature remains constant due to is high specific heat capacity and finally water filters out harmful ultra-violet rays from the sun. Water?s role in life of any organism is due to its physical and chemical properties. They strange properties of water allow it to act as an excellent solvent, to provide an excellent support mechanism, due to the cohesive forces of attraction between the molecules being so strong and unlike any other liquids that it is virtually incomprehensible. Waters role in the life of any organism is of the up most importance. Without it life would simply not exist. Life began it water, and although some life evolved to live on land, it still relies entirely on the fantastic substance that is water.

The Role of Water in Living Organisms 7.5 of 10 on the basis of 4366 Review.