Life and water




To understand why water is so vital to life and why NASA seeks out the presence of water before it searches for life, one needs to first take a look at the busy environment that exists within a living cell.

Observe the video on the right, produced by WEHI, which depicts some of the metabolic processes taking place every second in every cell in our body. Nutrients must be brought into the cell and waste products quickly removed. Now this sounds pretty simple, but without water this would be impossible. Water is a perfect solvent that allows for the rapid movement of nutrients and waste in and out of the cell.


Water's special properties enable it to dissolve nutrients and waste material to create an environment within the cell where small and large proteins, such as enzymes, can move about freely at mild temperatures. All chemical reactions that take place in living organisms rely on the ability reactants particles to move about. Water provides the aqueous environment for mobility of these reactants and so facilitates life sustaining processes.



Not only is the ability of water to dissolve polar molecules or ionic substances crucial to life, but its ability to repel non-polar (hydrophobic) molecules is also critical and results in the formation of cell membranes. An image of a molecule, known as a phospholipid, is shown on the right. It is this type of molecule that can arrange itself into a lipid-bilayer that surrounds and protects every cell.



Water is a very sticky substance and its particles display strong cohesive forces, that is, they will stick together relatively strongly, as well as exhibiting strong adhesive forces, that is, they can stick to most other surfaces.
Click to see a demonstration of these forces.
Why is this important?
This simple and overlooked property of water, strong cohesive and adhesive forces, makes it a very good coolant and an excellent solvent able to dissolve nutrients and carry them hundreds of meters up tall trees through a process known as capillary action.

Not only do living organisms use water to regulate body temperature through sweating, but powerful machines, such as modern day cars, use it as a coolant. This is because water can absorb an immense amount of heat energy before its temperature increases. This property alone makes it an essential defence against climate change as the vast oceans on the surface of the planet are huge heat sinks that moderate the surface temperature.
Amongst water's many roles which include, regulating Earth's climate and supporting life in its many forms are due to its size and molecular structure. The link below looks more closely at the chemistry of water and the relationship to its properties.
Let's take a closer look at the chemistry of this incredible compound.