In many different organisms it is common for substances to be in solution and for the water to be the solvent. Organisms that live underwater require oxygen to respire but do not need to rise to the surface to do so, instead they can breath underwater using the oxygen gases that are dissolved within the water.
All organisms are made primarily of water, jellyfish have the highest percentage of water component at 99% which helps to explain why many breeds of jellyfish are near on transparent, and the human body is 75% water, although there are great differences in the amounts of water, it is clear that water is in and involved in everything.
Water plays a vital role in the metabolism and photosynthesis. ‘It is the medium in which all metabolic reactions take place and is needed for hydrolysis (Further Studies In Biology). ’ Water is used in All cells for hydrolysis - the break down of a substance by water. Water is a medium for several chemical reactions, other than those already named, as well as this water is good for diffusion and osmosis, e.g. gaseous exchanges, which need to be moist as the exchange takes place in solution, which explains why the lungs are moist. Without this water the human species and all mammals for this fact would not be able to breath and therefore would not be able exist.
Blood consists mainly of water. Blood can be used in a variety of ways, primarily to transport oxygen around the body, to transport soluble food, hormones and waste. Plants act in a similar way to humans but instead of blood the plant has sap which does the same job . All of the substances I have listed are dissolved into the water which in turn means the products can be transported to where they required, quite like a taxi but much more important.
In the process of fertilisation water is particularly needed, semen which contains the sperm is mostly water hence the translucent colouring. Without this water the sperm would not be able to reach the ovum and could therefore not fertilise the egg. It provides a water-based environment for the reproductive cells and for the development of embryos in land-based species (Heinemann Advanced Science Biology).
Water is a helpful lubricant as it reduces the friction between two objects and eases movement. This is why joints like the shoulder socket and ball never touch, this is because the bone is cushioned by the water this fluid is known as the ‘synovial fluid’ .All internal organs are precious and if damaged cause serious problems often leading to death, this is why most organs are protected and lubricated by fluids (mostly water). The most important fluid is the ‘cerebro-spinal fluid’ which protects the brain. Water is also virtually impossible to compress adding to the factor it is a good protective fluid.
Water can also be used for support, it is well adapted for this role as its cohesive forces with in molecules. Plant cells have both a membrane and a cell wall, but if the plant cell becomes too full of water it does not burst as expected (unlike a balloon which would burst very quickly as there is no support) but instead the cell wall creates an equal force which makes the cell rigid which leads to support which is how plants have long stems. Also animals such as a worms, support is often provided by the pressure of the fluid inside them. This is the same for a hydrostatic skeleton.
Water is the ideal habitat for many organisms such as fish and other varieties of life forms, this is for a number of reasons, the first being that water can act as a protective shield, this shield does not protect the organism from predators but it stops the cells from dying out as they would on land. A fish would not live on land as it has not evolved enough to adapt to the surroundings. Water is important for cooling down mammals and hydrating organisms in dry environments without evaporating immediately this means that it 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 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.
Large expanses of water (seas/ oceans ect) have roughly the same consistent temperature (due to its high specific heat capacity) so few temperature control mechanisms are needed, water filters out harmful ultra-violet rays from the sun. The specific heat capacity for water is unusually high. It takes 4.2 joules of energy to heat 1g of water by 1 degree Celsius (www.biologymad.com). this means that aquatic organisms don’t have to quickly adjust to their surrounding habitat. 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).
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Water is also used as 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 changes as it becomes closer to 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).
All living organelles depend on water, both plants and mammals need water to survive. Without water the world would not be as we know it, not a single organism that would be able to survive as all reactions take place with in a aqueous solution.
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
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