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2010-01-27 17:27:04
Chapter 2 B

Cell Biology Chapter 2
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  1. Ionic bonds
    • An ion is an atom or molecule that has gained or lost one or more electrons
    • --It now has a net electric charge -- NaCl
    • Cations:net positive charge Ca++
    • Anions:net negative charge
    • Ionic bond:occurs when a cation binds to an anion
    • Positive and Negative come together
  2. Chemical Reactions
    • Occurs when one or more substances are changed into other substances
    • Reactants → products
    • Share many properties
    • All require a source of energy
    • Reactions in living organisms often require a catalyst (enzymes)
    • Tend to proceed in a particular direction but will eventually reach equilibrium
    • Occur in liquid environment - water
  3. Types of Reactions
    • Hydrolysis:reaction uses water to break apart covalent bonds
    • Also called catabolism (+)R1-R2 -> R1-H + R-2-OH (gives away)
    • Dehydration:reaction loses water to form bonds
    • Also called anabolsim (-)R1-H + R2-OH -> R1-R2 (accepts)
  4. Types of Reactions
    • Energy is released when a bond breaks (catabolism reaction) +
    • Energy is required to form a bond (anabolism reaction) -
  5. Properties of water
    • A solution is made up of the
    • Solvent: liquid
    • Solutes: substances dissolved in solvent
    • Aqueous solution: water is the solvent
    • Ions and molecules that contain polar covalent bonds will dissolve in water
  6. Hydrophillic
    • Hydrophillic: “water-loving”
    • --Readily dissolve in water
    • --Ions and molecules that contain polar covalent bonds
    • Hydrophobic: “water-fearing”
    • --Do not readily dissolve in water
    • --Nonpolar molecules like hydrocarbon
    • Amphipathic molecule: Have both polar or ionized regions at one or more sites and nonpolar regions at other sites
    • --May form micelles in water
    • --Polar (hydrophilic) regions at the surface of the micelle and nonpolar (hydrophobic) ends are oriented toward the interior of the micelle
  7. Water - Not just a solvent
    • Water has many important functions in living organisms
    • -Participates in chemical reactions
    • Hydrolysis or dehydration
    • -Provides force or support
    • -Remove toxic waste components
    • -Evaporative cooling
    • Cohesion and adhesion
  8. Acids & Bases
    • Acids:(-) are molecules that release hydrogen ions (H+) in solution
    • --A strong acid releases more H+ than a weak acid
    • --Evereything left behind is a negative
    • Bases:(+) lower the H+ concentration
    • --Some release OH-
    • --Others bind H+
  9. pH
    • Acidic (-) solutions are pH 6 or below
    • pH 7 is neutral
    • Alkaline (+) solutions are pH 8 or above
  10. The pH of a solution can affect
    • The shapes and functions of molecules
    • The rates of many chemical reactions
    • The ability of two molecules to bind to each other
    • The ability of ions or molecules to dissolve in water
  11. Buffers
    • Organisms usually tolerate only small changes in pH
    • Buffers help to keep a constant pH
    • An acid-base buffer system can shift to generate or release H+ to adjust for changes in pH

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