The Biological Importance Of Water
The Biological Importance Of Water";"The Biological importance of Water
Generally, the main biological importance of water is that life cannot exist without it. In fact on a percentage basis, the majority of any organism is comprised of water. Additionally, it is believed that life first originated in the bodies of water on the earth. The importance of water is seen in such third world countries as Kenya. Where the inhabitants are forced to drink water so dirty and contaminated that they know it might kill them. However they still drink it because it’s essential for life.
The solvent properties of water are essential for living organisms to survive. The solubility of the substances needed by the organism depends on the ability of water to interact with them, and the polarity of water plays a critical role.
Water is an excellent solvent for ionic compounds such as sodium chloride. This is because cations like sodium ions become surrounded by a shell of water molecules each attracted to the positive charge by the slight negative charge on the water-oxygen atoms. Anions are hydrated through the attraction of the slight positive charge of water-hydrogen atoms to their negative charge. Substances, inparticular polar substances, which dissociate in water, are known as hydrophilic.
Covalent compounds are harder for water to act as the solvent. Some molecules have strong intramolecular forces, which prevent their solution in water, but have charged surfaces, which attract a covering of water molecules. This covering ensures that the molecules remain dispersed throughout the water, rather than forming large aggregates, which could settle out. The dispersed particles and liquid around them collectively form a colloid. Such substances are sugar and alcohols. This is important because such molecules provide an osmotic effect, which helps to draw water into the blood vessels of living organisms.
The fact that water is a very effective solvent allows all of the substances essential for the functioning of cells and organisms (glucose, amino acids, vitamins, fats, respiratory gases) are transported around in solution in the blood. This means that water acts as a transport medium for the polar solutes. It carries things needed by cells to cells and products from cells to other cells and waste products to be excreted. In mammals this happens in the blood and in plants it happens in the xylem and phloem.
Similarly all metabolic reactions, catalysed by enzymes occur in solution. Chemicals can only react with each other...