The Importance of Water to Living Organisms

Water is a simple chemical compound, each molecule composed of one oxygen and two hydrogen atoms.

It is the most important biochemical of all. There would be no life on the planet whatsoever without the existence of water. Water can be found in all 3 states (gas, water and solid) naturally. Water molecules are dipolar (meaning that its electrons are not shared equally due to covalent bonding) and this generates hydrogen bonding between atoms. This raises its melting and boiling points. As a result its structure gives water many important properties such as its thermal, high surface tension, incompressibility and cohesiveness, which give it many useful biological roles such as being a solvent, a coolant, an insulator, as support, a lubricant and a reagent.

I am now going to talk about the properties of water. Water is attracted to other water. This is called cohesion. Water can also be attracted to other materials. This is called adhesion. The oxygen end of water has a negative charge and the hydrogen end has a positive charge. The hydrogen’s of one water molecule are attracted to the oxygen from other water molecules. This attractive force is what gives water its cohesive and adhesive properties. The forces between liquid molecules are responsible for surface tension (water has a very high surface tension). The do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed. This means that water is an excellent support mechanism in molecules. It also means that it is virtually incompressible; this means that water is a good protecting fluid.

Water is a good solvent due to its polarity. The solvent properties of water are vital in biology, because many biochemical reactions take place only within aqueous . When an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipoles of the water are attracted to positively charged components of the solute, and vice versa for the positive dipoles. Non polar molecules are insoluble in water. The result of this is a cluster of water molecules ...

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Water has thermal properties as well. As hydrogen bonding restricts the movement of water molecules, a relatively large amount of energy is needed to raise the temperature of water. This means that large bodies of water such as oceans and lakes are slow to change temperature as environmental temperature changes. As a result they are more stable habitats. Due to the high proportion of water in the body internal changes in temperature are also minimized, making it easier to achieve a stable body temperature. Since a relatively large amount of energy is needed to convert water to a gas, the process of evaporation transfers a correspondingly large amount of energy and can be a effective means of cooling the body, as in sweating and panting. Conversely, a relatively large amount of energy must be transferred from water before it is converted from a liquid to a solid (ice). This makes it less likely that water will freeze, which is an advantage both for the bodies of living organisms and for organisms which live in water.

Water is an unusual chemical because the solid form, ice, is less dense than its liquid form. Below 4ºC the density of water starts to decrease. Ice therefore floats on liquid water and insulates the water underneath it. This reduces the tendency for large bodies of water to freeze completely, and increases the chances of life surviving in cold conditions. Changes in density of water with temperature cause currents which help to maintain the circulation of nutrients in the ocean. Water is liquid at room temperature.

Water has a high specific heat index. This means that water can absorb a lot of heat before it begins to get hot. The high specific heat index of water helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden, especially near the oceans.

Water also has many uses. It is very important in transport. Blood is mainly made up of water and helps transport food, hormones, waste products (ammonia and urea) and oxygen, similarly in plants; sap is used to transport food and other substances. All these substances can easily be dissolved in water and then can be transported around the body or the plant. Water is also used during fertilization when sperm must reach the ovum; the sperm is transported in semen, which is mostly water. Water also surrounds many internal organs to give protection and lubrication like the pleural fluid around the lungs. Water can also be used for support. As plant cells have cell walls as well as cell membranes, when the plant cell becomes plasmolysed (due to osmosis) it will not burst but the cell wall exerts a force equal to the osmotic force (the cell is turgid) and this is important in the support of leaves

Water is a major component of cells, typically forming between 70 and 95% of the mass of the cell. In a cell water is used for hydrolysis, the breakdown of a substance by water e.g. polysaccharides to monosaccharide, forming a glycosidic bond; a medium for chemical reactions, due to its properties as a solvent; the diffusion and osmosis of substances, e.g. gaseous exchange, the surfaces the exchange is taking place over need to be moist as the exchange takes place in solution, therefore there is water in the lungs or in mesophyll cells (in plants).

Water has a low viscosity. This is useful as it allows it to flow easily through tubes e.g xylem vessels

In conclusion it is obvious to see from looking at all the properties and uses of water that living organisms have no chance of surviving without it.