Water

Water, also known as H2O, is made up of 2-parts hydrogen and 1-part oxygen. Water is a very important part of life and it makes up 71% of the earth’s surface, it is needed to sustain all life on this planet. As well as this on average 60% of the human body is made up of water, a heart and brain are composed of 73% water, the lungs are around 83% and even bones are made up of 31% water. Some of the important properties and functions of water will be explained within this essay to emphasise the biological significance of water. Water is a metabolite, a metabolite is a substance that is used within the chemical reactions that take place in a living organism in order to keep that organism alive, these chemical reactions are called metabolic reactions. However, most metabolic reactions take place in solutions, for example in prokaryotic and eukaryotic cells the cytoplasm’s metabolic reaction needs solution to take place, this particular reaction needs water. In a hydrolysis reaction a water molecule is needed to break a bond, it is also required in a condensation reaction as a molecule of water is released to form a new bond. Hydrolysis and condensation are involved in many metabolic reactions, the energy from ATP (Adenosine Tri-Phosphate) is released using hydrolysis. Condensation reactions are used to join amino acids together to from polypeptides, polypeptides are protein and the body needs protein to build and repair tissue.

Related imageIt is also a solvent which means certain substances can be dissolved into it, it is because of the waters polarity that is such a useful solvent. Water is polar as it has a positive end and a negative end, meaning that both ends attract the polar opposite ion this leads to the ions being totally surrounded by water therefore causing it to dissolve. A good example of this is salt, salt has a positive sodium ion and a negative chloride ion, the hydrogen in the water is positively charged so the negative ion (chloride) is attracted to it and the positive ion (sodium) is attracted to the oxygen. Water has a high latent heat of vaporization which means that a lot of energy is required for the hydrogen bonds between the water molecules to break. It is important that water has a high latent heat of vaporisation as this means living organisms can cool down without losing a significant amount of water, this is because of evaporation. Another factor that helps with temperature control is high specific heat capacity, this just means that water takes a lot of energy to heat up, this makes water a good habitat for living organisms as it is likely to be more stable underwater then it is on land. The water inside organisms manages to remain stable which helps the internal body temperature to maintain constant.

Another Important property of water is the cohesion between water molecules, this is the attraction between two molecules of the same type, because water is polar it is also very cohesive. Because water is a strong cohesive it is great for transporting substances, this also means that when water comes into contact with air it has a high surface tension. This means that due to the cohesive nature of the water molecules the surface of the water allows it to resist the external force of some objects even though they may have a higher density, for example a paperclip would float along the surface of the water even though the paperclip has a higher density than the water, this is due to the high surface tension.