2009-2010<br />The Chemistry of Life<br />
Why are we studying chemistry?<br />Chemistry is the foundation of Biology<br />
The World of Elements<br />H<br />C<br />O<br />N<br />P<br />S<br />Na<br />Mg<br />K<br />Ca<br />
Elements & their valence shells<br />Elements in the same column have the same valence & similar chemical properties<br />...
–<br />–<br />–<br />Chemical reactivity<br />Atoms tend to<br />complete a partially filled valence shell<br />          ...
–<br />–<br />H2 (hydrogen gas)<br />Covalent bond<br />Bonds in Biology<br />Hydrogen bond<br />H2O<br />Weak bonds<br />...
Nonpolar covalent bond<br /><ul><li>Pair of electrons shared equally by 2 atoms
example: hydrocarbons = CxHx
methane (CH4 )</li></ul>Lots of energy stored…& released<br />balanced, stable,good building block<br />
H<br />Oxygen<br />H<br />Polar covalent bonds<br /><ul><li>Pair of electrons shared unequally by 2 atoms
example: water = H2O
oxygen has stronger “attraction” for the electrons than hydrogen
oxygen has higher electronegativity
water isa polar molecule
+ vs – poles
leads to many interesting properties of water…</li></ul>+<br />–<br />–<br />–<br />–<br />+<br />
Hydrogen bonding<br />H bonds<br />H<br />H<br />O<br /><ul><li>Polar water creates molecular attractions
attraction between positive H in one H2O molecule to negative O in another H2O
also can occur wherever an -OH exists in a larger molecule
Weak bond
but common in biology</li></li></ul><li>2010-2011<br />Chemistry of Life<br />Properties of Water<br />
More about Water<br />Why are we studying water?<br />All life occurs in water<br /><ul><li>inside & outside the cell</li>...
Elixir of Life<br />Special properties of water<br />1.	cohesion & adhesion<br />surface tension, capillary action<br />2....
1. Cohesion & Adhesion<br /><ul><li>Cohesion
H bonding between H2O molecules
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20 ch02chemistry2010

  1. 1. 2009-2010<br />The Chemistry of Life<br />
  2. 2. Why are we studying chemistry?<br />Chemistry is the foundation of Biology<br />
  3. 3. The World of Elements<br />H<br />C<br />O<br />N<br />P<br />S<br />Na<br />Mg<br />K<br />Ca<br />
  4. 4. Elements & their valence shells<br />Elements in the same column have the same valence & similar chemical properties<br />Remember<br />some food chainsare built on reducing O to H2O<br />& some on <br />reducing S to H2S<br />
  5. 5. –<br />–<br />–<br />Chemical reactivity<br />Atoms tend to<br />complete a partially filled valence shell<br /> or<br />empty a partially filled valence shell<br />This tendency drives chemical reactions…<br />and creates bonds<br />
  6. 6. –<br />–<br />H2 (hydrogen gas)<br />Covalent bond<br />Bonds in Biology<br />Hydrogen bond<br />H2O<br />Weak bonds<br />hydrogen bonds<br />attraction between + and –<br />hydrophobic & hydrophilic interactions<br />interactions with H2O<br />van derWaals forces<br />ionic<br />Strong bonds<br />covalent bonds<br />sharing electrons<br />H2O<br />
  7. 7. Nonpolar covalent bond<br /><ul><li>Pair of electrons shared equally by 2 atoms
  8. 8. example: hydrocarbons = CxHx
  9. 9. methane (CH4 )</li></ul>Lots of energy stored…& released<br />balanced, stable,good building block<br />
  10. 10. H<br />Oxygen<br />H<br />Polar covalent bonds<br /><ul><li>Pair of electrons shared unequally by 2 atoms
  11. 11. example: water = H2O
  12. 12. oxygen has stronger “attraction” for the electrons than hydrogen
  13. 13. oxygen has higher electronegativity
  14. 14. water isa polar molecule
  15. 15. + vs – poles
  16. 16. leads to many interesting properties of water…</li></ul>+<br />–<br />–<br />–<br />–<br />+<br />
  17. 17. Hydrogen bonding<br />H bonds<br />H<br />H<br />O<br /><ul><li>Polar water creates molecular attractions
  18. 18. attraction between positive H in one H2O molecule to negative O in another H2O
  19. 19. also can occur wherever an -OH exists in a larger molecule
  20. 20. Weak bond
  21. 21. but common in biology</li></li></ul><li>2010-2011<br />Chemistry of Life<br />Properties of Water<br />
  22. 22. More about Water<br />Why are we studying water?<br />All life occurs in water<br /><ul><li>inside & outside the cell</li></li></ul><li>Chemistry of water<br />H2O molecules form H-bonds with each other<br />+H attracted to –O<br />creates a sticky molecule<br />
  23. 23. Elixir of Life<br />Special properties of water<br />1. cohesion & adhesion<br />surface tension, capillary action<br />2. good solvent<br />many molecules dissolve in H2O<br />hydrophilic vs. hydrophobic<br />3. lower density as a solid<br />ice floats!<br />4. high specific heat<br />water stores heat<br />5. high heat of vaporization<br />heats & cools slowly<br />Ice!I could use more ice!<br />
  24. 24. 1. Cohesion & Adhesion<br /><ul><li>Cohesion
  25. 25. H bonding between H2O molecules
  26. 26. water is “sticky”
  27. 27. surface tension
  28. 28. drinking straw
  29. 29. Adhesion
  30. 30. H bonding between H2O & other substances
  31. 31. capillary action
  32. 32. meniscus
  33. 33. water climbs uppaper towel or cloth</li></ul>Try that with flour…or sugar…<br />
  34. 34. How does H2O get to top of trees?<br />Transpiration is built on cohesion & adhesion <br />
  35. 35. 2. Water is the solvent of life<br /><ul><li>Polarity makes H2O a good solvent
  36. 36. polar H2O molecules surround + & –ions
  37. 37. solvents dissolve solutes creating solutions</li></li></ul><li>What dissolves in water?<br /><ul><li>Hydrophilic
  38. 38. substances have attraction to H2O
  39. 39. polar or non-polar?</li></li></ul><li>What doesn’t dissolve in water?<br /><ul><li>Hydrophobic
  40. 40. substances that don’t have an attraction to H2O
  41. 41. polar or non-polar?</li></ul>Oh, lookhydrocarbons!<br />fat (triglycerol)<br />
  42. 42. 3. The special case of ice<br /><ul><li>Most (all?) substances are more dense when they are solid, but</li></ul>not water…<br /><ul><li>Ice floats!
  43. 43. H bonds form a crystal</li></ul>Ice!I could use more ice!<br />And this hasmade all the difference!<br />
  44. 44. Why is “ice floats” important?<br /><ul><li>Oceans & lakes don’t freeze solid
  45. 45. surface ice insulates water below
  46. 46. allowing life to survive the winter
  47. 47. if ice sank…
  48. 48. ponds, lakes & even oceans would freeze solid
  49. 49. in summer, only upper few inches would thaw
  50. 50. seasonal turnover of lakes
  51. 51. sinking cold H2O cycles nutrients in autumn</li></li></ul><li><ul><li>H2O resists changes in temperature
  52. 52. high specific heat
  53. 53. takes a lot to heat it up
  54. 54. takes a lot to cool it down
  55. 55. H2O moderates temperatures on Earth</li></ul>Specific heat& climate<br />4. Specific heat<br />
  56. 56. Evaporative cooling<br />5. Heat of vaporization<br />Organisms rely on heat of vaporization to remove body heat<br />
  57. 57. Ionization of water & pH<br /><ul><li>Water ionizes
  58. 58. H+ splits off from H2O, leaving OH–
  59. 59. if [H+]= [-OH], water is neutral
  60. 60. if [H+]> [-OH], water is acidic
  61. 61. if [H+]< [-OH],water is basic
  62. 62. pH scale
  63. 63. how acid or basic solution is
  64. 64. 1 7  14</li></ul>H2O  H+ + OH–<br />
  65. 65. pH Scale<br />H+ Ion<br />Concentration<br />Examples of Solutions<br />pH<br />100<br />Hydrochloric acid<br />0<br />10–1<br />1<br />10–2<br />2<br />Stomach acid, Lemon juice<br />Vinegar, cola, beer<br />10–3<br />3<br />Tomatoes<br />10–4<br />4<br />10–5<br />5<br />Black coffee, Rainwater<br />10–6<br />6<br />Urine, Saliva<br />7<br />Pure water, Blood<br />10–7<br />Seawater<br />8<br />10–8<br />Baking soda<br />10–9<br />9<br />Great Salt Lake<br />10–10<br />10<br />10–11<br />Household ammonia<br />11<br />10–12<br />12<br />Household bleach<br />10–13<br />13<br />Oven cleaner<br />10–14<br />Sodium hydroxide<br />14<br />tenfold changein H+ ions<br />pH1  pH2<br />10-1 10-2<br />10 times less H+<br />pH8  pH7<br />10-8 10-7<br />10 times more H+<br />pH10  pH8<br />10-10 10-8<br />100 times more H+<br />
  66. 66. 9<br />8<br />7<br />6<br />Buffering<br />range<br />5<br />pH<br />4<br />3<br />2<br />1<br />0<br />1<br />0<br />3<br />4<br />5<br />2<br />Amount of base added<br />pH of cells must be kept ~7<br />pH affects shape of molecules<br />shape of molecules affect function<br />therefore pH affects cellular function<br />Control pH by buffers<br />reservoir of H+<br />donate H+ when [H+] falls<br />absorb H+ when [H+] rises<br />Buffers & cellular regulation<br />

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