Biology 1- Water

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Water plays an important role in plants and animals with key clements found in aqueous solution. Water acts as a medium for metabolic reactions. Water makes up between 65% and 95% by mass of most plants and animals. It is an important constituent of cells.

The most important property of water molecules is that they can 'stick together' by forming hydrogen bonds with other water molecules. Also, as it is a liquid, it provides a medium for molecules and ions to mix in. The hydrogen bonding of water molecules makes the molecules more difficult to separate and affects the physical properties of water.

Water as a solvent

Water is an excellent solvent. Because water has slightly positive and slightly negative parts, it will attract other charged particles, such as ions, and other polar molecules, such as glucose. This allows chemical reactions to take place in solution and since these chemicals dissolve in water, it acts as a transport medium e.g. in animals, blood transports many dissolved substances. Non-polar molecules such as lipids will not dissolve in water.

Thermal Properties

Water has a high specific heat - a large amount of heat energy is needed to raise the temperature of the water. This is because the hydrogen bonds between water molecules restrict their movement. This prevents large fluctuations in the temperature of water and this is particularly important in keeping the temperature of aquatic habitats stable so that organisms do not have to endure extremes of…


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