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Unformatted text preview: rginine phenylalanine aspartate lysine
leucine asparagine glutamate histidine serine valine Charge is dependent upon pH Stereo Isomers (Enantiomers)
20 amino acids used in protein synthesis
Group I: nonpolar Alanine (A)
Valine (V) Group II: polar Asparagine (N)
Tyrosine (Y) Group III: charged Arginine (R)
Aspartic Acid (D)
Glutamic Acid (E)
Lysine (K) Isomer ( “same unit ”): two molecules with the same molecular formula,
but arranged differently.
mirror image molecules.
“Right-handed ” [Dextro -]
“Left-handed ” [L evo -]
versions of the molecule. C
CH 3 L isomer L- Dopa Heyer H NH 2 NH 2 C H CH 3 D isomer D-Dopa 9 Biological Chemistry Stereo Isomers (Enantiomers) Peptide Bonds Link Amino Acids One of the great mysteries of the origin of living cells —
• All non-biological synthesis reactions of organic molecules produce
both D- and L- isomers in equal yield.
• And all non-biological reactions using organic molecules as reactants
react with both D- and L- isomers equally.
• Yet, living cells are constructed only of D-sugars and their derivatives,
and only L-amino acids and their derivatives! Peptide bond formation L- Dopa D-Dopa (biologically active) • Amino acids linked by dehydration synthesis
Æ “peptide bond”
• Polymer of amino acids = polypeptide
• Different polypeptides have different amino acid sequences (biologically inactive) Protein Shape Determines Function
• Specific 3-D shape
• Shape is critical to
function 3. Nucleic Acids — Information
& Energy Carrying Molecules
• Used for:
– Information (DNA, RNA)
– Cellular Energy (ATP) • Monomer:
– Nucleotide • Polymer:
• Denaturation = loss
of shape and function Nucleotides
• 5 possible types of Nitrogenous Base – Nucleic acid
Ribbon model of
lysozyme protein • 1, 2, or 3 phosphates off
#5 carbon of sugar Human chromosomes Nucleic Acids are linear polymers of
Nucleotide monomers • 2 possible types of C5 Sugar •Nucleotides to make RNA =
Ribose sugar + A, G, C, or U base
•Nucleotides to make DNA =
Deoxyribose sugar + A, G, C, or T base Heyer Condensation reaction between
•phosphate on #5 carbon of the sugar in one nucleotide, and
•the hydroxyl on #3 carbon of the sugar in the other nucleotide
Polymer forms sugar-phos...
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- Spring '10
- molecular biology