Water is the most abundant component in any organim, the lowest being in seeds (20%) and on the top of the scale, jellyfish (99% water) hence why they are transparent. Water is essential for the survival for all living organisms and is widely used for a lot of different reasons. For some organisms, water is vital to energise and carry out functions, but for other organisms, water is a form of habitat.
Role of water in reactions
Water is needed in a number of processes and as a fundamental component to some reactions. It is used in the break down and formation of nutrients and compounds; known as hydrolysis and dehydrations reactions. For example, in hydrolysis, the addition of water is needed. This is used when hydrolysing polysaccharides to monosaccharides or when converting proteins into amino acids.
A bi-product of respiration is water, this is useful for plants in desert or dry habitats/areas, as the water produced would play a big part in photosynthesis, to provide plant cells with raw materials. Plant cells need the water for photosynthesis to create glucose and also replace the lost electrons from the chlorophyll, as well as providing protons.
In reactions, water is also needed for the diffusions and osmosis of substances. For herbaceous plants, that remain upright, water is needed to increase pressure against the rigid cell wall using the process of osmosis. When this happens the plant is said to enter a state of ‘turgor’.
Role of water as a solvent
One reason why water is so essential is because it is a great solvent. Secretion of substances (hormones and digestive juices), nutrients and excretory products (urea and ammonia) can be transported in water, notably in the animal bloodstream and for plants, in the xylem and phloem vessels. Because water is slightly ionised, other polar molecules such as salts, sugars and amino acids readily dissolve in it. This is why more reactions take place while in solution with water. Solvents are useful for human digestion, when large starch molecules need to be broken down into soluble sugars. For plants, their method of obtaining mineral salts is by receiving them in solution. It is clear that water is excellent at providing an aqueous environment for molecules to dissolve and travel through/in.
Role of water in temperature regulation
Water does not change temperature very easily and has a very high heat capacity, making it a very useful substance for living organisms. Because of waters high heat capacity, it is able to absorb a lot of heat energy for its temperature rise, and loses a lot to cool. This helps to reduce temperature fluctuations in organisms, and also in aquatic environments, where water helps to keep a constant temperature. In terms of reducing temperature fluctuations in organisms, this can be especially helpful for large organisms in preventing them from becoming over-heated. For plants, evaporations…