The Roles of Water in the Lives of Living Organisms

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Water/H2O is the single most important molecule on the planet’s surface, without which life couldn’t exist. It is the most abundant compound on the planet and provides habitat for a large number of living organisms. It is also the most important component in the functioning of the human body with our bodies being around 70% water. A molecule of water consists of one oxygen atom and two hydrogen atoms that share pairs of electrons, making a covalent bond. However as oxygen has 8 protons compared to hydrogen’s 2, it attracts the electrons with a slightly greater force so oxygen becomes slightly negative and hydrogen becomes slightly positive. The presence of this unequal charge distribution means water is a dipolar molecule. Because of these polar (charged) parts of the molecule, it allows water to make weak hydrogen bonds with other water molecules. These intermolecular bonds are a result of the electrostatic attraction between the partially positive hydrogen on one molecule and the partially negative oxygen in another molecule. [1] One molecule of water is able to make a number of hydrogen bonds so it allows long chains of water molecules to stick together. This is called cohesion. These cohesive forces between molecules of water are responsible for the high surface tension of water. The molecules of water on the surface have fewer water molecules surrounding them since there is air above. This results in a stronger bond between those molecules that actually do come in contact with one another, and a surface layer of strongly bonded water. This creates a considerable barrier between the atmosphere and the water so certain objects can float without sinking below the surface. This is particularly useful for small insects, so that they can walk on water. The cohesive forces also make water a very good transport medium which is useful in the blood plasma of mammals
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