Water and inorganic ions

consists of one atom of oxygen chemically bonded to 2 atoms of hydrogen

polar molecule

the oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge

different poles attract and therefore the positive pole of one water molecule will be attracted to the negative pole of another water molecule. The attractive force between these opposite forces is a hydrogen bond

because water molecules stick together they require more energy to seperate them. For this reason the boiling point of water is higher than expected. Water therefore acts as a buffer against a sudden temperature variation

hydrogen bonding between water molecules means that it requires a lot of energy to evaporate 1g of water

the tendency for molecules to stick together is known as cohesion. with its hydrogen bonding water has large cohesive forces and these allow it to be pulled up through a tube such as the xylem vessel. In the same way where water molecules meet air they tend to be pulled back into the body of water rather than escaping from it (surface tension)

water is the main constituent of all living organisms. -mammals are typically 65% water

water is used to break down many complex molecules by hydrolysis

water readily dissolves other substances -gases -wastes -inorganic ions enzymes

-its evaporation cools organisms and allows them to control their temperature -it’s not easily compressed and therefore provides support -it’s transparent and therefore aquatic plants can photosynthesis

• very high specific heat capacity • very high latent heat of vaporisation • water as a solvent • cohesion • metabolic reactions

is a charged atom that does not contain carbon

in organisms where they occur in solution in the cytoplasm of cells and in body fluids as well as part of larger molecules

iron ions- transport of oxygen phosphate ions-structural role in DNA and storing energy in ATP# hydrogen ions- determining the pH of solutions and therefore functioning of enzymes sodium ions- transport of glucose and amino acids across plasma membranes

-High specific heat capacity -Buffer changes in temperature