Functions Of Water

Firstly, let`s start by talking about what water is. It is a dipolar molecule, meaning that it is a positive pole and a negative pole. It is made up of 2 atoms of Hydrogen and 1 atom of Water.

As water is dipolar, the positive pole of 1 water molecule will attract to the negative pole of another - this attraction is called a Hydrogen bond. Whilst each individual bond is weak, the collective force of all the Hydrogen bonds present makes water molecules stick together.

Due to this, water has a high specific heat capacity. It takes more energy to heat a specific amount of water as it takes more energy to break the bonds. This quality allows it to act as a buffer against rapid changes in temperature. As we as organisms are 65% water, it means that temperature changes for our body are also somewhat buffered.

Similarly they also have a high latent heat of vaporisation - it takes a lot of energy to evaporate 1g of water. This relates to the concept of sweating, as we are evaporating water by heat as a means to cool our body down.

Another property of water is it`s strong cohesive forces due to its Hydrogen bonding. The definition of cohesion is the tendency of molecules to stick with one another. This is present in plants as water is taken up during transpiration. Furthermore when we breathe, water molecules in our breath meet the air. At this interface, they tend to go back to the body of water (which in this case would be back inside the body) rather than go into the body of air. This concept can be applied when you see insects being able to stand on top of water. This is called surface tension, which means that each water molecule at the surface is bound tightly to the one next to it. Hence water can support a small amount of weight, such as the weight of an insect.

Now let`s talk about the different ways water is used in the living organism.

1) Water is used in Hydrolysis reactions to break other molecules down. It is also the product in condensation reactions. An example of this is that Water is used up in the production of ADP and is produced in the production of ATP.

2) It is used as a medium to allow chemical reactions to happen.

3) It is also used during photosynthesis to make glucose.

4) It can be used a solvent, so it dissolves other substances. For example: Oxygen, CO2, Ammonia, Urea, Inorganic Ions and some Enzymes.

5) It can be used in the process of sweating - thermoregulation of the body.

6) It is difficult to compress and hence acts as support in some living organisms, e.g. the turgor pressure in some plants.

7) It is completely transparent, and hence allows light to pass through so that plants in the water can photosynthesise. This feature is also what allows us to see, as the light rays will pass through the fluid in the eye to our retina.