كيمياء يروتين

• Proteins


  Most structurally & functionally diverse group of biomolecules
• Proteins


  2006-2007
• Proteins


  • Multipurpose molecules
  • Involved in almost everything
  • Function in Metabolism, Support, Transport, Regulation, Motion
• Enzymes


  Biological catalysts that speed up chemical reactions
• Digestive enzymes


  • Lipase
  • Amylase
  • Lactase
  • Protease
• Molecular biology enzymes


  • Polymerase
  • Ligase
• Industrial uses of proteins

  • Dairy, baby food, rubber, beer, photography, contact lens cleaner
• Structural proteins


  • Keratin - hair and nails
  • Collagen - supports ligaments, tendons, and skin
  • Silk - cocoons and spider webs
• Transport proteins

  • Channel and carrier proteins in the cell membrane
  • Allow substances to enter and exit the cell
  • Transport molecules in blood e.g. Hemoglobin
• Defense proteins


  • Antibodies combat bacteria and viruses
• Regulatory proteins


  • Hormones - intercellular messengers that influence metabolism e.g. Insulin, Human growth hormone
  • Receptor proteins - detect chemical signals in nerve cells

  
• Motion proteins


  • Muscle contraction - Actin and myosin
  • Motor proteins - allow cell components to move
• Amino acids


  • Monomers that make up proteins
  • 20 different amino acids
  • 12 made by body
  • 8 essential amino acids (must get from food)
• Polypeptide


  Polymer of amino acids

  
• Protein


  • One or more polypeptide chains folded and bonded together
  • Large and complex molecules with complex 3-D shape

  
• Proteins with complex 3-D structure

  • Rubisco
  • Hemoglobin
  • Growth hormones
• Amino acid structure


  • Central carbon (α carbon)
  • Amino group
  • Carboxyl group (acid)
  • R group (side chain) - variable group that confers unique chemical properties

  
• Types of amino acids

  • Nonpolar and hydrophobic
  • Polar or charged and hydrophilic
  • Sulfur containing - form disulfide bridges

  
• Building proteins


  1. Peptide bonds - linking NH2 of one amino acid to COOH of another

  2. N terminus - C terminus
• Protein structure and function


  • Function depends on 3-D structure
  • Twisted, folded, coiled into unique shape
• Primary (1°) structure


  • Order of amino acids in chain
  • Determined by gene (DNA)
  • Even one amino acid change can affect structure and function

  
• Secondary (2°) structure


  • Local folding along short sections of polypeptide
  • Interactions between adjacent amino acids
  • H bonds between backbones
  • α-helix and β-pleated sheet

  
• Tertiary (3°) structure


  • Whole molecule folding
  • Interactions between R groups - hydrophobic, disulfide bridges, ionic bonds, hydrogen bonds, van der Waals forces
  • Globular (spherical) proteins have tertiary structure
• Quaternary (4°) structure


  • Two or more tertiary folded peptide subunits bonded together
  • e.g. Hemoglobin - 4 polypeptides, Collagen - 3 polypeptides

  
• Denaturing proteins

  1. Unfolding a protein, disrupting 3° structure

  2. Caused by changes in pH or temperature

  3. Disrupts H bonds, ionic bonds and disulfide bridges

  4. Destroys functionality