The Biological Importance of Water

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The Biological Importance of Water

Water is a simple molecule, yet it is fundamental to life. For example

in active living cells, two-thirds, or often more, of the area is

occupied by water, and two-thirds of the globe is covered in water.

Water is therefore extremely abundant, and in biological terms it has

great importance both inside cells, and externally, for example as a

habitat.

Water is the most abundant component of any organism.

Humans are 60% water, and most organisms are 60-90% water. The lowest

water content can be found in plant seeds, and the highest in

jellyfish, and this is the cause of their transparency. The water is

found mainly in the protoplasm, and here it plays vital roles in many

functions, for example in metabolism in all organisms, and

photosynthesis and support in plants.

Substances produced in organisms often need to be transported to other

parts of the organism. In humans, blood is used to transport food,

hormones, oxygen, waste products and so on, and similarly in plants,

sap is used to transport food and other substances. Both of these

mediums for transports (blood and sap) are mainly water, as this is

the substance that can dissolve the products to be transported. Blood

allows oxygen to be transported to tissues, and waste products to be

quickly removed. It also allows the transport of hormones, to control

various organs.

Plant cells have a cell wall in addition to the usual cell membrane,

so the cells are not likely to burst, as can happen in animal cells

when too much water enters them by osmosis. Plant cells can therefore

become turgid - this occurs when water diffuses in the cell by osmosis

up to the point where the cell wall prevents further water intake, by

exerting a force equal to the osmotic force, by which the water was

diffusing in. This makes the cell stiff, or turgid. The turgidity of

plant cells in important in support, as it helps to support leaves,

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