1. From molecules to cells © 2007 Paul Billiet ODWSODWS

2. THE CELL Organelles CHLOROPLASTS, MITOCHONDRIA, NUCLEUS etc Supramolecular assemeblies ENZYME COMPLEXES, RIBOSOMES, CHROMOSOMES Macromolecules NUCLEIC ACID PROTEINPOLYSACCHARIDELIPID Building blocks NUCLEOTIDEAMINO ACID SIMPLE SUGARFATTY ACID & GLYCEROL Precursors from the environment CO 2, H 2 O, MINERALS The levels of organisation in cells © 2007 Paul Billiet ODWSODWS

3. Elements in living & non-living material EARTH’S CRUSTHUMAN TISSUES RANK ELEMENT% % 1stO62,5000H60,300 2ndSi21,2000O25,500 3rdAl6,4700C10,500 4thNa2,6400N2,450 5thCa1,9400Na0,730 6thFe1,9200Ca0,266 7 th Mg1,8400P0,134 8 th P1,4200S0,132 9 th C0,0800K0,036 10thN0,0001Cl0,032 © 2007 Paul Billiet ODWSODWS

4. Elements in living & non-living material EARTH’S CRUSTHUMAN TISSUES RANK ELEMENT% % 1stOxygen62,5000Hydrogen60,300 2ndSilicon21,2000Oxygen25,500 3rdAluminium6,4700Carbon10,500 4thSodium2,6400Nitrogen2,450 5thCalcium1,9400Sodium0,730 6thIron1,9200Calcium0,266 7 th Magnesium1,8400Phosphorus0,134 8 th Phosporus1,4200Sulphur0,132 9 th Carbon0,0800Potassium0,036 10thNitrogen0,0001Chlorine0,032

5. Water Formula H 2 O Structure Slightly (  ) negative at the oxygen end and slightly positive at the hydrogen end -- ++ ++ O HH © 2007 Paul Billiet ODWSODWS

6. The association between the polar water molecules Weak hydrogen bonds © 2007 Paul Billiet ODWSODWS

7. Comparing molecules -61-8634H2SH2SHydrogen sulphide +19-9220HFHydrogen fluoride +100018 H2OH2OWater -33-7817 NH 3 Ammonia -161-18416CH 4 Methane Boiling point / °C Melting point / °C Molecular mass FormulaMolecule Compared to molecules of similar size and properties water has a very high melting point and boiling point © 2007 Paul Billiet ODWSODWS

8. Thermal properties The molecules of water can absorb a lot of heat energy Water has a very high thermal capacity (4.2 J°C -1 g -1 ) The hydrogen bonding forms a lattice which does not easily fall apart as the temperature rises © 2007 Paul Billiet ODWSODWS

9. Thermal properties and life Water is a very, thermally stable medium Water helps living organisms resist changes in their environment To make water change from a liquid to a vapour requires a lot of energy Evaporation of water on a the surface of a body cools it down significantly © 2007 Paul Billiet ODWSODWS

10. African elephants (Loxodonta africana) bathing © Shirley Burchill 2007 © 2007 Paul Billiet ODWSODWS

11. Solvent properties The polar properties of water make it a good solvent for: Polar molecules (e.g. sugars and alcohols) These form hydrogen bonds with the water molecules Ionic compounds (e.g. salts, acids and bases) These dissociate into their component ions © 2007 Paul Billiet ODWSODWS

12. Solvent properties and life Water is a very important transport medium for living organisms because of its solvent properties and because it remains a liquid over a large range of temperatures Water is also an important medium for biochemical reactions © 2007 Paul Billiet ODWSODWS

13. Webvision

14. Cohesion The cohesion (stickiness) between water molecules Water molecules are also attracted to wettable surfaces Very tall thin columns of water can be supported before they break The tallest are at the physical limits of water trees (sequoia and eucalyptus are 100m tall) © 2007 Paul Billiet ODWSODWS

15. Giant red wood Sequoiadendron giganteum California USA Public Domain image Eucalyptus grandis NSW Australia Public Domain image

16. Surface tension Water molecules hold together forming a skin at the surface This is strong enough for some organisms to be supported Water Skater © Shirley Burchill 2007 Water skater Gerris gibbifer © 2007 Paul Billiet ODWSODWS

17. Density Water is densest at 4°C whilst it is still a liquid So ice floats on the surface of water Organisms which live in water do not risk freezing solid so easily Freezing is usually fatal Water forms a good habitat for living organisms Iceberg, Antarctica © Shirley Burchill 2007 © 2007 Paul Billiet ODWSODWS

18. Transparency Water is a transparent liquid, light passes though it Blue light, with the most energy, penetrates furthest, red light is the weakest and penetrates least Plants can photosynthesise under water Animals can use their visual systems Kelp forests (Macrocystis pyrifera) California © Mike Graham, Phycology Lab @ Moss Landing Marine Laboratories © Text 2007 Paul Billiet ODWSODWS