Protein Synthesis,
the molecular basis of gene expression

Proteins are polypeptides with biological significance.
Polypeptides are linear polymers of amino acids (AA's).
Amino acids consist of: H2N-CH-COOH

  • an amino group (H2N-)
  • an acid group (-COOH)
  • joined by a carbon (-CH-)
  • with a side chain (R) on the central carbon
    There are 20 different AA's defined by the R-groups
    . found in known eukaryotic organisms


    Polypeptides: . . H2N-CHR-CO-HN-CHR-CO-... -HN-CHR-COOH


    Proteins

  • structural
    . . - shape is important to structure
  • enzymatic
    . . - lock and key hypothesis: enzyme fits onto substrate
    . . - shape is important to function
    Shape is related to structure:
  • primary structure
    . . - sequence of AA's
    . . - locations of hydrogen-bonding sites
    Illustration of the importance of sequence
    headline
    MIJORITY APPROVE PRESIDENT'S POLICY
    possible corrections of single typo
    MAJORITY APPROVE PRESIDENT'S POLICY
    MINORITY APPROVE PRESIDENT'S POLICY
  • secondary structure
    . . - folding based on hydrogen-bonding sites
  • tertiary structure
    . . - higher level structure, including combining multiple polypeptides


    proteins are assembled by ribosomes

  • small half =
    . . - enzymatic protein
  • large half =
    . . - structural protein
    . . - enzymatic rRNA
    which do not know how to recognize AA's
    which is "plot material" ...


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    © 2004 Prof. LaFrance, Ancilla College