Biological Molecules - Water Flashcards
Describe the properties of water?
- polar,
- v shaped,
- cohesive,
- has extensive hydrogen bonding within itself,
- high specific heat capacity,
- high latent heat of vaporisation,
- high surface tension (due to cohesion),
- is a good solvent,
- is ideal transport medium,
- takes part in metabolic reactions, e.g hydrolysis and condensation reactions.
What does polar mean? Explain why water is polar?
- Polar means it is slightly charged at different ends (poles) of the molecule,
- Water is polar because it has slightly positive hydrogen atoms at one end and areas of negative charge, where the electrons are, at the other.
Describe the bonding between molecules in water?
Water molecules form weak hydrogen bonds to other water molecules. The water molecules are always twisting and rotating to try to match up positive hydrogen to the negative electrons. There is extensive hydrogen bonding, hence why water has a high specific heat capacity.
Why does water rise up xylem tubes?
Its cohesive nature means water sticks to the sides of the tube, then as the water at the sides bonds to the other water molecules the water at a lower level is slowly pulled upwards.
Define solvent? Why is water a good solvent?
Being a solvent means it dissolves substances to a great or lesser extent. Water does this by surrounding the ions of a substance and forming hydrogen bonds to the polar molecules. A positive ion would bond to the negative electrons (e.g Na+) whereas a negative ion would bond to the positive hydrogens (e.g Cl-)
What is the significance of water’s high latent heat of vaporisation to cooling mechanisms?
The mammalian cooling method of sweating is much more efficient because of the properties of water. Only a small amount of water is need e to remove a large amount of heat, meaning water is very effective for sweating.
What is the significance of water’s high specific heat capacity to aquatic life?
A large amount of energy is needed to increase the temperature of water. Conversely, a lot of energy must be lost from water for it to freeze. This creates a stable environment for aquatic life because they are unlikely to experience significant fluctuations in the temperature of their habitat.
