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The role and importance of water

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The role and importance of water Water is the most important molecule on Earth. Without it, life would not have begun. Water provided the essential oxygen to make Earth liveable on. It is a major component of cells, making up 70-95% of the mass of cells - and 96% in soft-bodied animals such as jellyfish. Water provides support; it works as transport, protection, and lubrication; provides a constant temperature and is an excellent habitat. Water, or H2O, is an unusual molecule as it can be found naturally in all three states, it is bonded covalently by hydrogen bonds. The oxygen is slightly negatively charged and the hydrogen slightly positive, therefore making the molecule 'polar'. This is a weak charge on its own, but is a large force when there are lots of water molecules together. This makes it difficult to separate the molecules. Having a boiling point of 100�C and a melting point of 0�C is unusual for a molecule of its size (waters relative molecular mass [RMM] is 18), because other molecules of a similar size such as Ammonia (RMM also 18) are gases at room temperature. This is due to the strong hydrogen bonds that don't want to break apart making the boiling point high. Water also has a high specific heat capacity, taking 4.2 Joules of energy to raise 1 gram of water by 1�C. ...read more.


Water plays a vital role inside cells, especially in photosynthesis and respiration. In plant cells it is used as a raw material for photosynthesis to make glucose, and in the plant mesophyll cells where moisture is needed for gas exchange. Water is also used in animals in the lungs, where oxygen is dissolved into it to transfer it through the alveoli into the bloodstream, and vice versa for carbon dioxide. Water is also used in hydrolysis and condensation reactions, which are used to turn polysaccharides into monosaccharides, and forming glycosidic bonds. Hydrolysis is essential to both animals and plants as it lets them make the most of stored food in long chains by making the chains smaller. Osmosis, diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration, is used in all cells to transport substances. It is used in root hairs to take up water for the plant in the transpiration stream, and in blood to let molecules into cells where needed. Plants have cell walls as well as membranes, and when the plants become full of water, turgid, due to osmosis they do not burst. This is because the cell wall exerts an equal force to the osmotic force. This provides support in the stems and leaves of herbaceous plants. Because of their polarity, water molecules are attracted to many surfaces making it able to enter very narrow spaces such as between cells due against the force of gravity. ...read more.


Inside the intestines is mucus that helps the food pass easily along to get digested by villi. Amniotic fluid is a serous liquid that is very important to foetuses whilst growing inside the womb, providing support and protection from the outside world. Water also provides a habitat. Aquatic animals can breathe due to oxygen dissolved in the water. Due to its solvency, nutrients can also be easily supplied and waste easily taken away, because of changes in the density of water with temperature, currents are formed which take away or bring in substances for organisms. Water is transparent; therefore photosynthesis can still take place, meaning that plants can live at the very bottom of the sea. Water filters out harmful UV rays, provides buoyancy and maintains roughly a constant temperature. Water is most dense at 4�C, and when it freezes the ice formed floats on the surface due to the lattice arrangement of its structure. Staying at 4�C the ice insulates the water and lets aquatic life continue without a huge temperature change causing devastation to animals that don't have temperature control. In conclusion, water's distinctive properties has made it undoubtedly one of the most important molecules on Earth. Water is useful in many ways, and even helped in the very beginning of life. Although some animals have now moved onto land or sky, all still rely on water in some way or another, such as food, protection or as a universal solvent. Sarah Lowman LVIWAL 1 ...read more.

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