2.4 Water and its functions Flashcards
Why is water described as dipolar
Because it has a hydrogen with a slight positive charge and oxygen with a slightly negative charge
What is a hydrogen bond
The attraction between opposite charges of water
The oxygen is attracted to the hydrogen of another water molecule, causing them to stick together
Important properties of water
- Specific heat capacity
- Latent heat of vaporisation of water
- Cohesion and surface tension in water
- Water as a solvent
- Water in metabolism
What is the specific heat capacity of water
Relatively high due to the sticking together of water molecules through hydrogen bonding, therefore it takes more energy than expected
What does water act as
A buffer against sudden temperature changes, making the aquatic environment a temperature-stable one
What is the latent heat vaporisation of water
Hydrogen bonding between water molecules means that it requires a lot of energy to evaporate 1 gram of water
What does the tendency of molecules of water to stick together called
Cohesion. With its hydrogen bonding, water has large cohesive forces and these allow it to be pulled through a tube, e.g. Xylem
Why is water important to living organisms
- Water in metabolism
- Water as a solvent
- Evaporation (sweating)
- Not easily compressed
- Transparent
Why is water important in metabolism
It is used to break down many complex molecules by hydrolysis, e.g. proteins to amino acids
Chemical reactions also take place in a aqueous medium
Water is a major raw material in photosynthesis
Why is water important as a solvent
Water readily dissolves other substances
Gases like Oxygen and Co2, wastes such as ammonia and urea, enzymes which reactions take place in solution
Why is the evaporation of water important to organisms
Its evaporation cools organisms and allows them to control their temperature
Why is water not being easily compressed important to organisms
It provides support, for example the hydrostatic skeleton of animals such as earthworm
Why is water being transparent important to organisms
Aquatic plants can photosynthesise and light rays can penetrate the jelly-like fluid that fills the eye and so reach the retina
