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Carbon and the Molecular Diversity of Life


									Carbon and the Molecular
    Diversity of Life
        Chapter 4
       Organic chemistry is the study of carbon
   Organic chemistry -- Branch of chemistry that
    specializes in the study of carbon compounds;
    includes most compounds important to life.
   Great variety of structures and functions of organic
    molecules are due to carbon’s ability of carbon to
    bond with itself and many other elements.
   Pioneers of organic chemistry began to synthesize
    organic compounds from inorganic molecules.
   Friedrich Wohler (1828) synthesized urea.
   Stanley Miller (1953) demonstrated the possibility that
    organic compounds could have been produced under
    the chemical conditions of primordial Earth.
Miller-Urey Apparatus
    Carbon atoms are versatile building blocks
   The kinds and number of bonds carbon
    will form are determined by its tetravalent
    electron configuration. (4 valence e-)
   Completes its outer energy shell by
    sharing valence electrons in four covalent
    bonds. (Not likely to form ionic bonds.)
   Carbon atom is a central point from which
    the molecule branches off into four
    directions; results in large, complex
   An organic molecule's 3-dimensional
    shape will affect its function.
   When carbon forms four single covalent
    bonds, the four e- orbitals angle from the
    carbon atom to form a tetrahedron.
            Variation in carbon skeletons.
   Carbon chains may vary in:
    •   Length.
    •   Shape (straight chain, branched, ring).
    •   Number and location of double bonds.
    •   Other elements covalently bonded to available sites.
   This variation in carbon skeletons contributes to
    the complexity and diversity of organic
   Hydrocarbons -- Molecules containing only carbon
    and hydrogen.
   Major components of fossil fuels produced from
    the organic remains of organisms living millions
    of years ago, though they are not prevalent in
    living organisms.
   Hydrocarbon chains are hydrophobic because the
    C-C and C-H bonds are nonpolar.
   Isomers -- Compounds with
    the same molecular formula
    but with different structures
    and different properties.

   1. Structural isomers --
    Isomers that differ in the
    covalent arrangement of
    their atoms.
   Number of possible isomers
    increases as the carbon
    skeleton size increases.
   May also differ in the
    location of double bonds.
                   Isomers (cont)
   Geometric isomers --
    Same covalent
    relationships, but
    differ in spatial
   Result from the fact
    that atoms cannot
    rotate freely around
    double bonds.
   Subtle differences
    between isomers
    affects their biological
                   Isomers (cont)
   Enantiomers -- Isomers
    that are mirror images of
    each other.
   When four different atoms
    or groups of atoms are
    bonded to the same carbon
    (asymmetric carbon).
   Two different spatial
    arrangements of the four
    groups are mirror images.
   Usually one form is
    biologically active and its
    mirror image is not.
   L-isomer (levo/left)
   D-isomer (dextro/right)
Thalidomide: Very different
    Functional groups also contribute to the
           molecular diversity of life

   Functional groups -- Small groups of atoms
    bonded to the carbon skeleton of organic
    molecules. T
   Functional groups:
   • Have specific chemical and physical
   • Are commonly the chemically reactive regions
    of the molecule.
   • Behave consistently from one organic
    molecule to another.
   • Depending upon their number and
    arrangement, determine chemical properties of
    organic molecules in which they occur.
                Hydroxyl Group (R--OH)
   Functional group that
    consists of a hydrogen
    atom bonded to an
    oxygen atom, which in
    turn is bonded to carbon.
   Is a polar group (O-H
    bond is polar covalent).
   Makes the molecule to
    which it is attached water
   Hydrogen bonds form
    between polar water
    molecules and hydroxyl
   Organic compounds with
    hydroxyl groups are
    called alcohols.
                    Carbonyl Group
   Functional group that
    consists of a carbon atom
    double-bonded to oxygen (-
   Is a polar group (O can
    hydrogen bond)
   Molecules with this functional
    group are water soluble.
   Is a functional group found in
   If carbonyl is at the end off
    the carbon skeleton, the
    compound is an aldehyde.
   If the carbonyl is NOT at the
    end of the carbon skeleton,
    the compound is a ketone.
                    Carboxyl Group
   Functional group that
    consists of a carbon atom
    which is both double-bonded
    to an oxygen and single-
    bonded to the oxygen of a
    hydroxyl group.
   Is a polar group and water
   Since it donates protons,
    this group has acidic
   Compounds with this
    functional group are called
    carboxylic acids.
                 Amino Group
   Functional group that
    consists of a nitrogen atom
    bonded to two hydrogens
    and to the carbon skeleton.
   Is a polar group and soluble
    in water.
   Acts as a weak base; the
    nitrogen can accept a
   Organic compounds with
    this function group are
    called amines.
                 Sulfhydryl Group
   Functional group
    which consists of an
    atom of (- sulfur
    bonded to an atom of
    hydrogen SH).
   Help stabilize the
    structure of proteins.
   Organic compounds
    with this functional
    group are called thiols.
                    Phosphate Group
   Functional group in which
    the phosphate is attached to
    carbon skeleton by O.
   Loss of two protons leaves
    the phosphate group with a
    negative charge; has acid
   Polar group and soluble in
   Organic phosphates are
    important in cellular energy
    storage and transfer (ATP).
   1 C: methane           Propanol
   2 C: ethane (C-C)       (C-C-C-OH)
   3 C: propane           Propanal/Acetone
    (C-C-C)                 (C-C-C=O)

   Ethene (C=C)
   Ethyne (C=C)

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