Water Water is the medium in which all reactions take place in living cells. Materials are moved across body in watery medium. Water is a major habitat (oceans, rivers, ponds and lakes) 70% of the body is water.
Properties of water Water molecule is slightly polarised - slight negative charge (in oxygen atom) and slight positive charge (in hydrogen atoms) Because of this dipole, water molecules can form hydrogen bonds. Due to this water molecules 'stick together' Therefore water has a high melting and boiling points (it takes more energy to overcome the attractive forces of hydrogen bonds)
Properties of water Water is excellent solvent Water has one of the highest known surface tensions Water molecule is amphoteric (Water can act both as an acid ad as a base)
Emulsions and Suspensions Water insoluble substances form emulsions or suspensions Emulsions are tiny droplets of one liquid suspended in another liquid Suspensions are formed when a solid is mixed with a liquid and particles will separate out in the mixture is not constantly stirred.
Emulsions and Suspensions Blood is a suspension of cells in plasma. Fats are usually transported as emulsions in a watery medium.