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Chapter 2

Chapter 2. The Chemical Context of Life. You Must Know. The three subatomic particles and their significance. The types of bonds, how they form, and their relative strengths. Element “ pure ” substance Can ’ t be broken down by “ ordinary ” means to another substance

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Chapter 2

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  1. Chapter 2 The Chemical Context of Life

  2. You Must Know • The three subatomic particles and their significance. • The types of bonds, how they form, and their relative strengths.

  3. Element “pure” substance Can’t be broken down by “ordinary” means to another substance Ex. hydrogen (H), nitrogen (N) Compound 2 or more different elements combined in a fixed ratio Ex. H2O, CO2

  4. Elements of Life • 25 elements • 96% : C, O, H, N • ~ 4% : P, S, Ca, K & trace elements (ex: Fe, I) Hint: Remember CHNOPS

  5. II. Atomic Structure • Atom = smallest unit of matter that retains properties of an element • Subatomic particles:

  6. Mass # (protons + neutrons) 4 2 He symbol Atomic # (protons or electrons)

  7. Isotopes • # neutrons varies, but same # of protons • Radioactive isotopes used as tracers (follow molecules, medical diagnosis) • Uncontrolled exposure causes harm

  8. III. Chemical Bonds Strongest Bonds: • Ionic: 2 ions (+/-) bond (givers/takers) • Na+Cl- • affected by environment

  9. III. Chemical Bonds Strongest Bonds: • Covalent: sharing of e- • Polar: covalent bond between atoms that differ in electronegativity • Nonpolar: e- shared equally; eg. O2 or H2

  10. Weaker Bonds: • Hydrogen: H of polar covalent molecule bonds to electronegative atom of other polar covalent molecules

  11. Weaker Bonds: • Van der Waals Interactions: slight, fleeting attractions between atoms and molecules close together • Weakest bond • Eg. gecko toe hairs + wall surface

  12. Bonds

  13. All bonds affect molecule’s SHAPE affect molecule’s FUNCTION • Similar shapes = mimic • morphine, heroin, opiates mimic endorphin (euphoria, relieve pain)

  14. Chemical Reactions • Reactants Products • Eg. 6CO2 + 6H2O  C6H12O6 + O2 • Some reactions are reversible: • Eg. 3H2 + N2 2NH3 • Chemical equilibrium: point at which forward and reverse reactions offset one another exactly • Reactions still occurring, but no net changein concentrations of reactants/products

  15. Ch. 3 What property of water allows a water strider to “walk” on water? Contrast adhesion and cohesion. Give an example of each. Contrast hydrophobic and hydrophilic substances. Give an example of each.

  16. You Must Know • The importance of hydrogen bonding to the properties of water. • Four unique properties of water, and how each contributes to life on Earth. • How to interpret the pH scale. • The importance of buffers in biological systems.

  17. 1. Polarity of H2O • O- will bond with H+ on a different molecule of H2O = hydrogen bond • H2O can form up to 4 bonds

  18. 2. Properties of H2O • Cohesion = H-bonding between like molecules • Surface Tension = measure of how difficult it is to break or stretch surface of liquid

  19. 2. Properties of H2O • Adhesion = bonding between unlike molecules • Adhesion of H2O to vessel walls counters ↓ pull of gravity

  20. 2. Properties of H2O C. Transpiration= movement of H2O up plants • H2O clings to each other by cohesion; cling to xylem tubes by adhesion

  21. 3. Moderation of temperature Heat = Total amount of KE in system Temperature = measure intensity of heat due to average KE of molecules Which has higher temp? More heat?

  22. 3. Moderation of temperature • Water’s high specific heat • Change temp less when absorbs/loses heat • Large bodies of water absorb and store more heat  warmer coastal areas • Create stable marine/land environment • Humans ~65% H2O  stable temp, resist temp. change

  23. 3. Moderation of temperature • Evaporative Cooling • Molecules with greatest KE leave as gas • Stable temp in lakes & ponds • Cool plants • Human sweat

  24. 3. Moderation of temperature • Insulation by ice– less dense, floating ice insulates liquid H2O below • Life exists under frozen surface

  25. 4. Solvent of life • Solution = liquid, homogeneous mixture of 2+ substances • Solvent = dissolving agent (liquid) • Solute = dissolved substance • Water = versatile solvent

  26. 4. Solvent of life • “like dissolves like”

  27. 5. Acids and Bases H2O H+ + OH- (gains proton) H+ + H2O  H3O+ (hydronium ion) (loses proton) H2O – H+  OH-(hydroxide ion)

  28. 5. Acids and Bases Acidic Basic 7 14 0 pH Scale • Acid= increases H+ concentration (HCl) • Base= reduces H+ concentration (NaOH) • Most biological fluids are pH 6-8

  29. Figure 3.10 The pH scale and pH values of some aqueous solutions

  30. 5. Acids and Bases Buffers = substances which minimize changes in concentration of H+ and OH- in a solution (weak acids and bases) • Buffers keep blood at pH ~7.4 • If blood drops to 7 or up to 7.8, then death Carbonic Acid & Bicarbonate: important buffers in blood plasma

  31. Ocean acidification threatens coral reef ecosystems CO2 mixed with seawater  Carbonic acid (lowers ocean pH)

  32. Chapter 4 Carbon and the Molecular Diversity of Life

  33. You Must Know • The properties of carbon that make it so important.

  34. I. Importance of Carbon • Organic chemistry: branch of chemistry that specializes in study of carbon compounds • Organic compounds: contain Carbon (& H) • Major elements of life: CHNOPS • Carbon can form large, complex, and diverse molecules

  35. II. Diversity of Carbon • It has 4 valence electrons (tetravalence) • It can form up to 4 covalent bonds • Most frequent bonding partners: H, O, N

  36. II. Diversity of Carbon Bonds can be single, double, or triple covalent bonds.

  37. II. Diversity of Carbon • Carbon can form large molecules • 4 classes of macromolecules: carbohydrates, proteins, lipids, nucleic acids

  38. II. Diversity of Carbon Molecules can be chains, ring-shaped, or branched

  39. II. Diversity of Carbon • Forms isomers • Molecules have same molecular formula, but differ in atom arrangement • different structures different properties/functions

  40. Drug manufacturing: • Thalidomide = • “good” enantiomer reduce morning sickness • “bad” enantiomer  cause birth defects • “good” converts to “bad” in patient’s body • Now used to treat cancers, leprosy, HIV

  41. Fig. 4.8 The pharmacological importance of enantiomers

  42. III. Functional Groups • Behavior of organic molecules depends on functional groups • Most common functional groups: • Hydroxyl • Carbonyl • Carboxyl • Amino • Sulfhydryl • Phosphate • Methyl

  43. Functional Groups

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