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The Biological Importance of Water
The biological importance of water is due to its unique properties, such as its high polarity, ability to form hydrogen bonds, and high heat capacity, which make it essential for a variety of biological processes, including maintaining cellular structure, regulating temperature, and facilitating metabolic reactions. Keep reading for more detailed A-level Biology revision notes
Introduction
- Water is the basis of life on our planet. It exists in different physical states – solid, liquid and gas – and makes up 70% of the surface of Earth, plus 65 – 90% of the weight of all living organisms. Water also plays an important role in all vital processes of living organisms.
- The water molecule, H 2 O, is composed of one oxygen atom and two hydrogen atoms. These atoms are bound covalently (by a covalent bond). In a water molecule, hydrogen carries a positive molecular charge, while oxygen carries a negative molecular charge . Thus, a water molecule is a ‘polar’ molecule, because it has both positive and negative poles.
1- Water is a polar solvent.
- Water is regarded as the ‘general solvent’ or ‘universal solvent’ due to the polarity of its molecules. For example , when sodium chloride (NaCl) dissolves in water, it produces positive sodium ions and negative chlorine ions. The positive oxygen atoms in water attract the negative chlorine ions, and the negative hydrogen atoms attract the positive sodium ions. All polar substances (substances containing ions) can dissolve in polar solvents, such as water.
- All the essential substances for living organisms (vitamins, salts, amino acids, gases, and glucose) transport inside their bodies in the form of solutes dissolved in water. These substances take part in metabolic reactions inside the cells.
2- Water has the ability to ionize molecules, which are necessary for life.
- This means that water has the ability to disassociate the molecules necessary for life into positive and negative ions (water can do so due to the polarity of its molecules). For example , the pancreas secretes sodium bicarbonate (NaHCO 3). This compound ionizes in water into positive hydrogen ions and negative bicarbonate ions, which makes the medium alkaline and thus suitable for the enzymes’ work.
3- Water has high specific heat.
- Specific heat is the amount of heat required to increase the temperature of one gram of matter by 1 degree Celsius.
- Water has the highest specific heat on Earth due to the hydrogen bonds between its molecules.
- As a result of having high specific heat, water needs a great amount of energy to increase its temperature and loses a great amount of energy when its temperature decreases. This helps living organisms to have a constant temperature which is essential for the vital processes occurring within their bodies. Cells contain lots of water to keep their temperature constant.
- Animals and plants lose water by sweating and transpiration processes to decrease their temperature.
- The high specific heat of water provides living organisms with temperatures suitable for life on Earth.
- Water forms almost 70% of the surface area of Earth. If water didn’t exist in such a great amount, the temperature of the Earth would decrease dramatically because the substances forming the Earth’s crust have low specific heat.
- The water that makes up oceans absorb a great number of sun rays in the morning and spread them into the atmosphere at night in order to keep the temperature of the Earth suitable for living organisms.
4- Water has low viscosity and high surface tension.
- Surface tension is the cohesion of the molecules on the surface of a fluid to occupy the least possible volume. Viscosity is the resistance of a fluid to flowing.
- Water has low viscosity and high surface tension due to the hydrogen bonds between its molecules; these conditions are suitable for life.
These properties are important because:
1- They work on the cohesion of cell substances.
2- It slows down water loss in plants’ leaves through pores.
3- Some insects can walk on water due to the cohesion of the molecules on its surface.
5- Water density decreases under 4 ◦ C.
- Water expands when its temperature becomes less than 4 ◦ C (instead of shrinking). THis decreases its density and makes it float. In frozen lakes, we find ice on the surface, while we find liquid water underneath.
- This property is because of the hydrogen bonds between water molecules.
- This property is important because it enables living organisms to live in oceans and seas. Without this property, all oceans and seas will turn into ice, rather than just the surface. Surface freezing works as an insulator to prevent the rest of water from freezing.
6- The freezing point of water decreases if it has substances dissolved in it.
- This property is very important for living organisms, as it prevents the water in the cells of from freezing when exposed to temperatures less than 0◦C.
7- Water can turn into vapour in temperatures lower than boiling point (100◦C).
- Water vapour formed on the surfaces of oceans is carried by convection currents to cold layers in the atmosphere. This changes into clouds which provide living organisms with rain and water.
8- Water rise in capillary tubes.
- Water has the ability to rise in capillary tubes without being pumped and in opposition to external forces such as gravity. This property helps water transport from trees’ roots to all of its parts.
Read more about the structure and properties of water
Frequently asked question
What is the percentage of water in the human body.
An adult human body has almost 60% water in it.
What are the important biological functions of water?
Some of the important biological functions of water are:
Regulation of body temperature
Protection of important body organs like the brain
Moistening of mucosal surfaces
Why is water called a universal solvent?
Water has the ability to dissolve a number of substances (solutes) in it because of its polar nature. That’s why it is called a universal solvent.
How does water help in the temperature regulation of the human body?
Water has a high heat capacity. It means it can absorb a lot of temperature before heating up . That is how it helps in the regulation of body temperature.
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AS and A-level Biology
- Specification
- Planning resources
- Teaching resources
- Assessment resources
- Introduction
- Specification at a glance
- 3.1 Biological molecules
- 3.3 Organisms exchange substances with their environment
- 3.4 Genetic information, variation and relationships between organisms
- 3.5 Energy transfers in and between organisms (A-level only)
- 3.6 Organisms respond to changes in their internal and external environments (A-level only)
- 3.7 Genetics, populations, evolution and ecosystems (A-level only)
- 3.8 The control of gene expression (A-level only)
- Scheme of assessment
- General administration
- Mathematical requirements and exemplifications
- AS practical assessment
- A-level practical assessment
3.1.7 Water
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Essay 14: The biological importance of water
- Created by: bethanythomas101
- Created on: 10-04-18 15:21
The biological importance of water:
- Structure (Dipolar, Hydrogen bonds)
- Solvent (Hydrophobic/phillic interactions, proteins, nucleic acids, diffusion of molecules, dilution of toxic compunds- urea)
- Osmosis and turgidity (Effect on plants)
- Transport medium (Xylem, phloem, blood, lymph, secretion, excretion)
- High heat capacity (Temperature regulation)
- High heat of vapourisation (Cooling effect- sweating…
- Whole Syllabus
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IMAGES
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Join now →. The biological importance of water is due to its unique properties, such as its high polarity, ability to form hydrogen bonds, and high heat capacity, which make it essential for a variety of biological processes, including maintaining cellular structure, regulating temperature, and facilitating metabolic reactions.
An example AQA Biology A-Level synoptic essay for the title "The ways in which water and the regulation of water content are important in organisms" Top band standard (25/25). Intended to be used as an example essay for inspiration and not to be copied under any circumstances.
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Fullscreen. The biological importance of water: Structure (Dipolar, Hydrogen bonds) Solvent (Hydrophobic/phillic interactions, proteins, nucleic acids, diffusion of molecules, dilution of toxic compunds- urea) Osmosis and turgidity (Effect on plants) Transport medium (Xylem, phloem, blood, lymph, secretion, excretion) High heat capacity ...
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