1.3.1.1 State that the most frequently occurring chemical elements in living things arecarbon, hydrogen, oxygen and nitrogen. Review ionic, covalent and hydrogen bonds Some fun with elementshttp://en.wikipedia.org/wiki/File:CHONPS.

2. 3.1.2 State that a variety of other elements are needed by living organisms, includingsulphur, calcium , phosphorus, iron and sodium http://commons.wikimedia.org/wiki/File:Electron_shell_020_Calcium.svg http://commons.wikimedia.org/wiki/File:Electron_shell_016_Sulfur.svg http://commons.wikimedia.org/wiki/File:Electron_shell_015_Phosphorus.svg http://commons.wikimedia.org/wiki/File:Electron_shell_026_Iron.svg http://commons.wikimedia.org/wiki/File:Electron_shell_011_Sodium.svg 3. http://www.flickr.com/photos/csb13/1873194745/ 4. 3.1.3 State one role for each of the elements Sulphur is an important element in some amino acids. It allows disulphide bonds to form in proteins, influencing the proteins shape see HL 7.5 Proteins What about iron?http://commons.wikimedia.org/wiki/File:Granulated_sulphur02.jpg 5. Iron is inhaemoglobin, tocarry oxygen inblood.Calcium?http://www.flickr.com/photos/csutka/3956855512/ 6. Calcium isin Bones!Sodium? http://www.flickr.com/photos/mugley/3491817141/ 7. Sodium isimportantfor nerveimpulsesSee Core6.5.5 Phosphorus?http://commons.wikimedia.org/wiki/File:Nametal.JPG.jpg 8. Phosphorus is in ATP 9. And, of course, in phospholipids in cell membranes.Here in Italian, just for a change.See: Structure of the membrane 2.4.1 http://commons.wikimedia.org/wiki/File:Fosfolipide.svg 10. and inDNA, amongst otherthings. Also CHON!http://commons.wikimedia.org/wiki/File:DNA_Structure%2BKey%2BLabelled.png 11. 3.1.4 Draw and label a diagram showing the structure of water molecules to show their polarityand hydrogen bond formation.Water is a weird andfreaky substance.It is this way becauseof its polar nature. http://commons.wikimedia.org/wiki/File:Water_drop_animation_enhanced_small.gif 12. No,that kindhttp://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg 13. The oxygen atom has 8Revisit the Crash Course positive charges (protons)Biology video Carbon (on at its nucleus.slide 2) at the 8:08 markTherefore it attracts the shared electrons more strongly and they spend more time orbiting the O -ve than the H. O Thus water molecules are polar, i.e. they have a negatively charged pole+ve H (the oxygen) and a positively charged pole (the hydrogens) H+ve 14. Hydrogen bonds form when the negatively charged oxygen on one molecule is electrostatically attracted to the positive hydrogen on anotherhttp://commons.wikimedia.org/wiki/File:Liquid_water_hydrogen_bond.png 15. 3.1.5 Outline the thermal, cohesive and solvent properties of water Thermal: You know about the phases (states) of water: Solid, Liquid and Gas. Water changes from solid to liquid and gas progressively as more energy (heat) is added. The weird thing about water is that it takes more energy than it should to change from one state to the next. Why do you think that might be? http://www.flickr.com/photos/westy559/328563694/ 16. Extra energy is requiredto overcome thehydrogen bondsWe say that water has avery high specific heatcapacityIt absorbs a lot ofenergy before changingstate http://commons.wikimedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.svg 17. CohesiveThe polar nature of water makes it stickyThe molecules themselves stick together dueto hydrogen bonds (cohesion)Water molecules stick to othersubstances, e.g. glass (adhesion) for the samereason If water did not have this cohesive nature then it would not form into drops like in the background. Drops form because the cohesive forces are trying to pull the water into the smallest possible volume, a sphere. 18. SolventWater is sometimes called the universal solventAgain, this is to do with the polar nature of waterConsider the sodium chloride below. The sodium andchloride atoms are held together by ionic bonds.NaCl DissolvingNaClhttp://commons.wikimedia.org/wiki/File:Sodium-3D.pnghttp://commons.wikimedia.org/wiki/File:Sodium-chloride-3D-ionic.png 19. Chlorine WaterSolvent SodiumThe polar water molecules have a stronger affinity forboth Na+ and Cl- than those ions do for each other.So the Na and Cl dump each other and drift off withthe water moleculesNaCl DissolvingNaCl 20. The polar water molecules have a stronger affinity for both Na+ andCl- than those ions do for each other.So the Na and Cl dump each other and drift off with the watermolecules.Note how on the right of the diagram the oxygen in each watermolecule is close to the Na+ and the hydrogen in the watermolecules is close to the Cl- NaCl DissolvingNaCl 21. All your ion arebelong tous!!! Also, the relatively small size ofCheck out the animation the water molecules means that they can gang up on the ions (not to scale)http://commons.wikimedia.org/wiki/File:Water_molecule.svg 22. 3.1.6 Explain the relationship between the properties of water and its uses in living organisms asa coolant, medium for metabolic reactions and transport mediumWaters thermal properties, itshigh specific heat, means that itcan cool us.Evaporating sweat (waterchanging phase from liquid to gas)takes heat away from the bodyWater is also the main componentof blood plasma.It transfers heat from the internalorgans to the skin.http://www.flickr.com/photos/bukutgirl/205304794/ 23. Cohesion allows plants to pullwater up their xylem viatranspirationAdhesion aidscohesion indrawing waterup due tocapillary actionSee HL Plant Science 9.2.6 http://www.flickr.com/photos/jaxxon/37559138/ 24. Waters solvent propertiesmean that waste and nutrientscan be moved around by blood in the veins and arteries.It enables trees to transport gases and solutes as wellhttp://www.flickr.com/photos/roughgroove/3554305017/ 25. Waters nature as a solventmeans substances dissolved in it can react with oneanother. The main component of cytoplasm, where many reactions occur, is water. http://www.flickr.com/photos/cambridgeuniversity-engineering/5431155934/ 26. Extension: Water as habitat These water striders rely on the cohesivenature of waterresulting in surfacetension http://www.flickr.com/photos/alexyo1968/4985953786/ 27. Liquid water IceWhat are the implications of ice being less dense(due to its highly organised crystalline structure) than liquid water?http://commons.wikimedia.org/wiki/File:Liquid-water-and-ice.png 28. Back to the bear I have somewhere tostand and hunt.See 5.2.6 to see why you hoomans are worrying me!http://commons.wikimedia.org/wiki/File:Eisb%C3%A4r_1996-07-23.jpg 29. Imagine ifice sankinstead offloated http://www.flickr.com/photos/toniblay/52925332/ 30. Lakes at high latitudes would freeze from the bottomup. Solid. And remain so for most if not all of the year athigh latitudes. The seas would be similarly affected. The water that is usually insulated by the ice, at above freezing temperatures, would not exist.There would be no habitat for the bottom dwellers.In fact, the pressure of the overlying water would makethe water at the bottom freeze. Even in the tropics. 31. Lucky for uswater is the way it is! 32. Further information: Properties of water Three of the best sites for IB-specific Biology information. The top link takes you to the PPT by Stephen Taylor