A large proportion of the mass of living organisms is due to water. Water makes up 65-70% of the mass of mammals.Water provides a habitat for many organisms.Water is used in metabolic reactions such as hydrolysis.Water is the medium in which all cellular reactions take place. The cytoplasm of all cells is mainly water.Water is a polar solvent and readily dissolves gases such as oxygen and carbon dioxide, waste products such as urea, enzymes and inorganic ions needed for metabolism. It is therefore a good transport medium.Blood plasma is water with dissolved substances and blood cells.Water is a coolant because of its high latent heat of vaporisation. Evaporation of water in sweat causes cooling.Water is not easily compressed so it provides turgor pressure which supports plants and animals such as the earthworm.Water is transparent so it transmits light so aquatic plants can carry out photosynthesis.
The Importance of Water
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Specification: AQA Biology (7401), AS-level, 3.1.7 Water. Topic: Nucleic Acids.
Key terms in this lesson
- hydrolysis
- The breaking of a covalent bond within a molecule using a water molecule.
- latent heat of vaporisation
- The energy needed to evaporate 1 kg of a liquid without a change in temperature.
- turgor pressure
- The pressure exerted by the contents of a plant cell against the cell wall as water enters by osmosis, making the cell rigid.
More in Nucleic Acids
- ATP
- ATP Synthesis
- Roles of ATP
- Water and Hydrogen Bonding
- Specific Heat Capacity of Water
- Latent heat of Vaporisation of Water
- Cohesion and Surface Tension of Water
- Inorganic Ions
All 18 lessons in Nucleic Acids · All AQA AS-level Biology topics