Water helps to give life and to save life. It provides a water-based environment for the reproductive cells and for the development of embryos in land-based species (Heinemann Advanced Science Biology). So if it wasn’t for water in the reproductive organs, and in the eggs of reptiles and birds, no land animals would be able to reproduce and there would be no animals or human beings on earth today. Water is also responsible for saving the lives of living organisms underwater as well as on land: the solid form of water, ice, is less dense than the liquid. This unusual property allows frozen water to float on the surface of rivers, lakes, oceans and ponds, acting as an insulating layer to stop the rest of the water underneath from freezing. Thus allowing living organisms below the surface of water to survive below freezing temperatures. However, if ice formed from the bottom up, freshwater life would only be found in those areas where the water never freezes (Heinemann Advanced Science Biology). This would have a devastating effect on the world, as animals’ food chains would be ruined with no fish or aquatic life forms.
Water molecules are also known to play a vital part in ensuring that amino acids bond together in the right way to make a protein. Proteins are extremely important in cells because they control key functions such as acting as catalysts for chemical reactions in the membrane and being receptors that enable hormones and nerve transmitters to bind to specific cells. Research at the Ruhr University of Bochum, Germany proved that hydrogen in water molecules trapped within the protein’s structure broke when exposed to infrared light. This triggered a chain of events in which fragments of some water molecules and clusters of other interacted to move protons through protein (New Scientist magazine). If water did not help to create proteins then many cells would be useless in a lot of ways. Cells would not be able to carry water-soluble molecules such as glucose for energy, there would be no pumps to move water-soluble molecules and ions in and out of the cell, and cells would have less adhesion to one another. These are just a few ways in which the absence of water in a living cell would be damaging and shows how important it really is.
The specific heat capacity for water is unusually high. It takes 4.2 joules of energy to heat 1g of water by 1 degree Celcius (www.biologymad.com). This is of great advantage to cells, aquatic organisms, and the environment in general because it provides an environment that takes a lot of energy to warm up because it is thermally stable. This thermal stability means that aquatic organisms don’t have to quickly adjust to their habitat suddenly changing in temperature as the sea and other large bodies of water stay at a remarkable constant temperature. This thermal stability is also seen within the water-based protoplasm of individual cells, and allows the biochemistry of life to be carried out at a fairly constant rate (Heinemann Advanced Science Biology).
The latent heat of vaporisation for water is very high because of the hydrogen bonds that need to be broken before the liquid water can become a gas. This is very beneficial to the Earth because it means that there is a large volume of water left on its surface, not vaporised and disappearing into the atmosphere. Having a high temperature for vaporisation in water is also very useful for organisms in dry or desert environments where there is very little rain. A lot of heat energy is used up in the evaporation of water, and this can be put to good use as a cooling mechanism. The sweating mechanism of the mammals has capitalised on this particularly (Heinemann Advanced Science Biology). Water is important for cooling down mammals and hydrating organisms in dry environments without evaporating immediately. Water also prevents the inside of cells from freezing as the latent heat of fusion of water is high, so it takes a lot of energy to melt and form ice. Consequently, it is unlikely that the contents of cells will freeze in cold conditions. It is very important that water stops living cells from freezing because the formation of ice in cells, with the accompanying increase in its volume, is almost always damaging if not fatal (Heinemann Advanced Science Biology).
Water is also used a kind of communication between DNA and protein in living organisms with cells containing DNA. The concentration of water around DNA corresponds with biological activity and undergoes radical changes as it nears the surface of the DNA. It seems that water molecules linger longer and rotate more slowly around base pairs that form a double helix than others. If water molecules linger longer around some base pairs than others, the level of hydration will mirror the sequence of base pairs (New Science magazine), dictating the order in which amino acids are knitted together to make proteins. This way the water molecules communicate to the protein the DNA sequence while it is still quite far away and can even warn the approaching protein about problems with the DNA before it arrives. If DNA is distorted due to some defect it becomes more hydrated and the protein can’t make proper contact (Monika Fuxreiter of the Hungarian Academy of Sciences Biological Research Centre in Budapest, New Science magazine). This is another reason why water is so important to living organisms; it can prevent serious problems from occurring in cells if DNA has a defect, which could save a whole animal, plant or human being’s life.
Life depends on water. Plants and animals alike need water survive and it is a vital part of all living organisms and the processes of life. Without water a living organism would not survive because all chemical reactions that take place in a cell are in an aqueous solution. Without water’s extraordinary properties aquatic life would not survive, or it would at least be a struggle, as water turns to ice and becomes an insulating layer for under-water life and its high latent heat of fusion prevents the contents of cells freezing to death, not to mention the thermal stability water provides in large bodies of water due to its high heat capacity. It is for certain that water is the most important and valuable part of living organisms as it helps to form protein in cells, a substance that a living cell could not function without, and can even prevent defects and mutations in cells by warning on-coming protein of potentially defected DNA.
Bibliography
Heinemann Advanced Science Biology
Ann Fullick
New Scientist magazine
8th April 2006-10-01
Issue no. 2546
www.biologymad.com
AS Biochemistry
A2 AQA Biology Specification A
Further Studies In Biology
Margaret Baker, Bill Indge, Martin Rowland
1,412 words
