Water Flashcards
Water
Water is a dipole.
It is a medium in metabolic reactions and a constituent of cells.
Makes up 65-95% of body mass.
Dipole
A dipole is a polar molecule with a slightly positive and negative charge separated by a small distance.
Water Properties: high density
This is good for aquatic organisms as it provides support and buoyancy.
It is also a good insulator and prevents large bodies of water from freezing and losing heat. Therefore organisms beneath can survive.
Water properties: cohesion
Water molecules attract each other and form hydrogen bonds.
Individually these bonds are weak, but, as there are so many they stick together and form a lattice.
This is cohesion.
Water properties: high surface tension
Has highest surface tension (other than mercury).
In a pond, the cohesion between water molecules on the surface allows it to support the body of an insect.
E.g pond skater
Water prop: high latent heat of vapourisation
Lots of energy is needed to change water from a liquid to a gas.
THIS IS IMPORTANT FOR TEMPERATURE CONTROL as the heat is used to vaporise water from sweat on skin/leafs surface.
As this water evaporates the body cools.
Water: high specific heat capacity
A large amount of heat energy is needed to change the temperature of a body of water. This is because hydrogen bonds restrict the movement of water molecules. Resisting increase in energy.
This prevents fluctuation in water temps, good for aquatic habitats.
This also allows enzymes to work in cells efficiently.
Water prop: metabolite
Water is a metabolite.
It is used in many biochemical reactions as a reactant and product.
E.g. in hydrolysis to split a molecule
Maltose+water—
Water properties: Solvent
Water is the best solvent. This is because water molecules are dipoles, attracting charged particles like ions and other polar molecules like glucose.
These then dissolve in water so chemical reactions can take place in solution.
Non-polar molecules can not dissolve in water. E.g. lipids
Water properties: transparency
Water is transparent allowing light to pass through. This is good for aquatic plants to photosynthesise.
