1.3.9 Water
Importance of Water to Organisms
The three states of water
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Water
Cells and body fluids are made up of 70% to
95% Water
Water has physical and chemical properties
that have important effects on organisms.
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Physical properties of water
• It is slow to heat up and cool down – kept at
a fairly steady temperature – helps to keep a
constant rate of metabolism.
• A good absorber of energy. It absorbs a lot
of heat as it evaporates, so sweating and
transpiration cools animals and plants. This
helps to keep temperature steady.
• Participates in the movement of material in
and out of cells.
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• Controls cell shape.
Chemical properties of water
• It is a universal solvent for transporting
substances in blood or in plants
• The medium for metabolism i.e. chemical
reactions take place in it within cells
• It is a reactant/product in chemical reactions
e.g. photosynthesis, respiration and
digestion
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Learning check
What are the physical properties of water?
• It is slow to heat up and cool down …
• A good absorber of energy …
• Movement of material …
• Cell shape …
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Learning check
What are the chemical properties of water?
• Universal solvent …
• Medium for metabolism …
• Reactant in chemical reactions …
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Need to know
Five good reasons why water is important for
organisms.
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END
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