Biology 107 Macromolecules II

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Biology 107Macromolecules II

• September 9, 2002

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Macromolecules II

• Student Objectives As a result of this lecture
  and the assigned reading, you should understand
  the following
• 1. Proteins are biological polymers constructed
  from amino acid monomers. Each different protein
  has a unique structure and function, and protein
  diversity is based upon these different
  arrangements of a universal set of amino acids.
• 2. There are seven major functional classes of
  proteins 1) structural proteins 2) contractile
  proteins 3) storage proteins 4) defense
  proteins 5) transport proteins 6) signaling
  proteins 7) enzymes.

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Macromolecules II

• 3. Amino acids have the same basic structure,
  with the amino group and carboxyl group bonded
  to a central C atom (the alpha C). This central
  carbon also has an attached H atom and a chemical
  group called the "R" group.
• It is the "R" group that is the variable part of
  the amino acid and determines the specific
  properties of each of the 20 amino acids in
  proteins.
• Amino acids are linked together by dehydration
  synthesis, with the resulting covalent linkages
  called peptide bonds.

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Macromolecules II

• 6. The specific shape that determines a protein's
  function comprises four (4) successive levels of
  structure, each determined by the previous level.
  
• a. The primary structure is the sequence of
  amino acids forming the polypeptide chain.
• b. The secondary structure consists of
  polypeptide chain coils or folds held in place
  by hydrogen bonding between the - N - H and the
  - C O groups along the backbone of the chain.
  Coiling or folding of a polypeptide chain
  usually results in one of two repeating
  structures, either an alpha-helix or a
  beta- pleated sheet.

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Macromolecules II

• Tertiary structure is the overall 3-dimensional
  shape of a polypeptide tertiary structure is
  maintained by bonding (hydrogen, ionic and
  covalent disulfide bridges) and hydrophobic or
  hydrophilic interactions between the "R" groups
  of various amino acids in the polypeptide chain.
• Quaternary structure is produced by the bonding
  interactions of two (2) or more polypeptide
  subunits. Quaternary structure is maintained by
  hydrogen bonding, ionic interactions, and
  hydrophobic interactions.

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Structure of Amino Acids with Nonpolar R Groups
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Structure of Amino Acids with Polar or Ionic R
Groups
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Primary Protein Structure
Consist of sequence of amino acids Has a polarity
amino end (1 amino acid of the chain) and
carboxyl end Dictates the other levels of folding
and structure
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Secondary Protein Structure
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Bonds That Stabilize Tertiary Structure
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Quaternary Protein Structure
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Summary of Levels of Protein Structure