20 ch02chemistry2010
- 1. 2009-2010The Chemistry of Life
- 2. Why are we studying chemistry?Chemistry is the foundation of Biology
- 3. The World of ElementsHCONPSNaMgKCa
- 4. Elements & their valence shellsElements in the same column have the same valence & similar chemical propertiesRemembersome food chainsare built on reducing O to H2O& some on reducing S to H2S
- 5. –––Chemical reactivityAtoms tend tocomplete a partially filled valence shell orempty a partially filled valence shellThis tendency drives chemical reactions…and creates bonds
- 6. ––H2 (hydrogen gas)Covalent bondBonds in BiologyHydrogen bondH2OWeak bondshydrogen bondsattraction between + and –hydrophobic & hydrophilic interactionsinteractions with H2Ovan derWaals forcesionicStrong bondscovalent bondssharing electronsH2O
- 7. Nonpolar covalent bondPair of electrons shared equally by 2 atoms
- 8. example: hydrocarbons = CxHx
- 9. methane (CH4 )Lots of energy stored…& releasedbalanced, stable,good building block
- 10. HOxygenHPolar covalent bondsPair of electrons shared unequally by 2 atoms
- 11. example: water = H2O
- 12. oxygen has stronger “attraction” for the electrons than hydrogen
- 13. oxygen has higher electronegativity
- 14. water isa polar molecule
- 15. + vs – poles
- 16. leads to many interesting properties of water…+––––+
- 17. Hydrogen bondingH bondsHHOPolar water creates molecular attractions
- 18. attraction between positive H in one H2O molecule to negative O in another H2O
- 19. also can occur wherever an -OH exists in a larger molecule
- 20. Weak bond
- 21. but common in biology2010-2011Chemistry of LifeProperties of Water
- 22. More about WaterWhy are we studying water?All life occurs in waterinside & outside the cellChemistry of waterH2O molecules form H-bonds with each other+H attracted to –Ocreates a sticky molecule
- 23. Elixir of LifeSpecial properties of water1. cohesion & adhesionsurface tension, capillary action2. good solventmany molecules dissolve in H2Ohydrophilic vs. hydrophobic3. lower density as a solidice floats!4. high specific heatwater stores heat5. high heat of vaporizationheats & cools slowlyIce!I could use more ice!
- 24. 1. Cohesion & AdhesionCohesion
- 25. H bonding between H2O molecules
- 27. surface tension
- 28. drinking straw
- 29. Adhesion
- 30. H bonding between H2O & other substances
- 31. capillary action
- 32. meniscus
- 33. water climbs uppaper towel or clothTry that with flour…or sugar…
- 34. How does H2O get to top of trees?Transpiration is built on cohesion & adhesion
- 35. 2. Water is the solvent of lifePolarity makes H2O a good solvent
- 36. polar H2O molecules surround + & –ions
- 37. solvents dissolve solutes creating solutionsWhat dissolves in water?Hydrophilic
- 38. substances have attraction to H2O
- 39. polar or non-polar?What doesn’t dissolve in water?Hydrophobic
- 40. substances that don’t have an attraction to H2O
- 41. polar or non-polar?Oh, lookhydrocarbons!fat (triglycerol)
- 42. 3. The special case of iceMost (all?) substances are more dense when they are solid, butnot water…Ice floats!
- 43. H bonds form a crystalIce!I could use more ice!And this hasmade all the difference!
- 44. Why is “ice floats” important?Oceans & lakes don’t freeze solid
- 45. surface ice insulates water below
- 46. allowing life to survive the winter
- 47. if ice sank…
- 48. ponds, lakes & even oceans would freeze solid
- 49. in summer, only upper few inches would thaw
- 50. seasonal turnover of lakes
- 51. sinking cold H2O cycles nutrients in autumnH2O resists changes in temperature
- 53. takes a lot to heat it up
- 54. takes a lot to cool it down
- 55. H2O moderates temperatures on EarthSpecific heat& climate4. Specific heat
- 56. Evaporative cooling5. Heat of vaporizationOrganisms rely on heat of vaporization to remove body heat
- 57. Ionization of water & pHWater ionizes
- 58. H+ splits off from H2O, leaving OH–
- 59. if [H+]= [-OH], water is neutral
- 60. if [H+]> [-OH], water is acidic
- 61. if [H+]< [-OH],water is basic
- 62. pH scale
- 63. how acid or basic solution is
- 64. 1 7 14H2O H+ + OH–
- 65. pH ScaleH+ IonConcentrationExamples of SolutionspH100Hydrochloric acid010–1110–22Stomach acid, Lemon juiceVinegar, cola, beer10–33Tomatoes10–4410–55Black coffee, Rainwater10–66Urine, Saliva7Pure water, Blood10–7Seawater810–8Baking soda10–99Great Salt Lake10–101010–11Household ammonia1110–1212Household bleach10–1313Oven cleaner10–14Sodium hydroxide14tenfold changein H+ ionspH1 pH210-1 10-210 times less H+pH8 pH710-8 10-710 times more H+pH10 pH810-10 10-8100 times more H+
- 66. 9876Bufferingrange5pH43210103452Amount of base addedpH of cells must be kept ~7pH affects shape of moleculesshape of molecules affect functiontherefore pH affects cellular functionControl pH by buffersreservoir of H+donate H+ when [H+] fallsabsorb H+ when [H+] risesBuffers & cellular regulation