Life and Chemistry: Small Molecules

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Life and Chemistry Small Molecules
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Atoms

• fundamental units of matter
• composed of smaller subatomic particles
• protons
• electrons
• neutrons

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Atoms

• atoms form elements
• 92 naturally occurring elements
• every element has
• atomic number
• atomic mass number

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Atoms

• isotopes
• same atomic number, different mass number
• radioisotopes

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Electron Location

• energy levels or electron shells?
• Why concern ourselves with electrons?

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Chemical Bonds

• Why do atoms interact?
• valence shell
• interact to form chemical bonds
• molecule
• compound

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Covalent Bonds

• sharing of electrons
• equal or unequal sharing
• dependent upon electronegativity of atoms
• may share multiple pairs of electrons

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Types of Covalent Bonds

• nonpolar covalent bonds
• equal sharing
• polar covalent bonds
• unequal sharing
• results in opposing partial charges at each end
  of the bond

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Hydrogen Bonds

• not actually a bond, but an attraction between
  opposite partial charges of two polar molecules
• very weak singularly, but strong in large numbers
• aid in shaping molecules

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Ionic Bonds

• form when one interacting atom is much more
  electronegative than the other
• one atom loses electrons, the other gains
  electrons
• strongest bond
• If ionic bonds are the strongest bond, why are
  living things made primarily of molecules that
  form covalent bonds?

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Ionic Bonds

• dissociate in water
• cation
• anion

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Polar and Nonpolar Interactions

• interact best with themselves
• hydrophobic
• hydrophilic

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Chemical Reactions

• change in chemical composition by forming or
  breaking chemical bonds
• reactants
• products

½

H2
O2
H2O
PRODUCTS
REACTANTS
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Chemical Reactions

• energy
• never created or destroyed, only transformed
• calorie

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Water

• great medium for life b/c
• 1. melting and freezing
• high specific heat
• high heat of fusion
• high heat of vaporization
• ice floats

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Water

• 2. cohesive and adhesive
• surface tension
• 3. an excellent solvent
• solution
• solvent
• solute

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Acids and Bases

• acid
• H donor
• HCl H Cl-
• base
• H acceptor
• NH2 H NH3

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Dissociation of Water

• 2 H2O ? H3O OH-
• rare
• 1500,000,000 in pure water dissociate

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pH

• ion product of water
• H OH- 1 x 10-14 M
• pH is the measure of the H in solution
• pH - log H

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Buffers

• maintain pH at a relatively constant level
• HCO3- H H2CO3
• law of mass action

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Properties of Molecules

• organic vs. inorganic
• functional groups
• isomer
• structural
• geometric
• optical

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