Describe the properties of water that make it important in living organisms.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Water makes up a large proportion of the bodies of living organisms and is involved in many biological processes. Scientists studying life in extreme environments note that liquid water is considered essential for life.
Model answer (5 marks)
Water is a universal solvent – many substances dissolve in it, allowing them to be carried in solution.
Water transports dissolved substances throughout the body.
Water acts as a reactant in many biochemical reactions, for example hydrolysis during digestion.
Water has a high specific heat capacity, so large amounts of energy are required to change its temperature.
Evaporation of water from surfaces (sweating) removes heat, cooling the body.
Water transports dissolved substances throughout the body.
Water acts as a reactant in many biochemical reactions, for example hydrolysis during digestion.
Water has a high specific heat capacity, so large amounts of energy are required to change its temperature.
Evaporation of water from surfaces (sweating) removes heat, cooling the body.
Examiner tips
- Use the exact terms: solvent, transport, reactant, high heat capacity, evaporation cooling.
- Show the logical link between each property and its biological role.
- Keep each point brief – 1–2 sentences per mark.
- Use UK spelling (e.g. 'behaviour').
Common mistakes
- Confusing water’s role as a solvent with it being a reactant – they are separate properties.
- Forgetting to mention the cooling effect of evaporation.
- Using vague language such as 'important' instead of specific properties.
Mark scheme (5 marks)
- Water is a solvent / many substances dissolve in water
- Dissolved substances can be transported around the body / water transports substances in solution
- Water is a reactant in chemical reactions such as digestion / hydrolysis
- Water has a high heat capacity / large amounts of energy needed to change its temperature
- Evaporation of water from surfaces causes cooling / sweating cools the body
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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