Importance of Water for Life
Water is the basis of life. There are various properties of water that make it basis of life. These include its molecular polarity, high specific heat, its boiling and melting points which allow it to remain liquid in most environments on Earth, its acid-base neutrality, small molecular size and low chemical reactivity.
Water as solvent
It serves as fundamental solvent for the chemical reactions in living organisms and is the main means of substance transportation between cells and tissues. It is responsible for correct temperature for life of an organism and is either regent or product of chemical reactions. All important macromolecules are produced by dehydration synthesis and broken down by hydrolysis.
Water in Human Body
Water makes around 65% of human body mass. It makes 90% of our brain, 85% of muscles and 25-40% of bones. Children have a greater proportion of water in their body in comparison to elders.
Polarity of Water
In water, two hydrogen atoms are attached to one central atom of oxygen by covalent bond, making an angular spatial structure. Since the hydrogen atoms lend electrons to the oxygen; oxygen atom becomes more negative while the hydrogen atoms become more positive. The spatial geometry of water makes it thus a polar molecule with negative and positive poles. If a molecule is polar, it will be attracted to other polar molecules. This can affect a wide range of chemical interactions, including whether a substance will or will not dissolve in water, the shape of a protein, and the complex helical structure of DNA.
Water and working of a microwave Oven
Water is the most common example of a polar molecule and that is also the reason that when we put a potato in a paper plate in a microwave, potato gets hot but not the paper plate. If we put the potato in a wet paper plate, it would get cooked along with Potato.
The implication of water being a polar molecule is that it works as an excellent solvent for polar substances because the electrical activity (attraction and repulsion) of its poles helps in the separation and the mixing of these substances, giving them more movement and thus increasing the number of molecular collisions and the speed of chemical reactions. On the other hand, water is not a good solvent for non-polar substances.
Water Soluble and Fat Soluble Substances
Water-soluble substances are polar molecules, meaning that they have electrically charged areas. Fat-soluble substances are non-polar molecules, meaning that they are electrically neutral.
Role of Water for Enzyme Activity
There can be no enzyme activity without water. The enzymes need water and correct pH to do their job. The pH is result of release of hydrogen cations (H⁺) and hydroxyl anions (OH⁻) by the acids and bases in water solutions.
Significance of heat capacity of water
The specific heat of water is 1 cal/gram °C. This implies that there is 1°C per gram change in its temperature per every addition or subtraction of 1 cal of energy. This is a very high value (compare it with ethanol that has 0.58 cal/g°C, and mercury that has 0.033 cal/g°C). This feature of water makes it an excellent thermal protector against temperature variations. Even if there is a sudden external temperature change, the internal biological conditions are kept stable in organisms containing enough water.