• An amino acid is amphiprotic (have both acid and base)

             o    Some are polar, non polar, acidic or basic

• List of amino acids (red are non-polar, yellow are polar, green are acidic, blue are basic, starred are essential)

•  An amino acid is amphiprotic (have both acid and base)

             o    Some are polar, non polar, acidic or basic

•  List of amino acids (red are non-polar, yellow are polar, green are acidic, blue are basic, starred are essential)

 
                o    Glycine (gly)
                o    Alanine (ala)
                o    Valine (val)*
                o    Leucine (leu)*                                                                                    
                o    Isoleucine (ile)*
                o    Methionine(met)*
                o    Phenylalanine(phe)*
                o    Tryptophan (trp)*
                o    Proline (pro)

               o    Serine (ser)

               o    Threonine(thr)*
               o    Cysteine (cys)
               o    Tyrosine (tyr)

               o    Asparagines (asn)
               o    Glutamine (gln)
               o    Glutamic Acid (glu)
               o    Aspartic Acid (asp)

              o    Lysine (lys)*
              o    Arginine (arg)

              o    Histidine (his)

Properties of Amino Acids

Peptide Bond - bond between the acid group of one amino acid and the amino group of another
Dipeptide - 2 amino acids joined by a

peptide bond

• Coded for by DNA and created by the ribosomes
• Proteins are long, flexible and able to form different links with themselves or other molecules
• Have an amino(A)-terminus and a Carboxyl(C)-terminus

Protein Structure

• A Protein's function depends on its shape which depends on its amino acids

• Primary Structure
  • Long chain of amino acids linked by covalent peptide bonds à in specific order
• Secondary Structure
  • Intermolecular forces (mostly H-bonds) cause the chain to coil into an α-helix or fold into a β-pleated sheet
• Tertiary Structure
  • Chaperone proteins help a growing polypeptide fold into its tertiary structure
  • Supercoiling due to polarity, the shape of the amino acids (e.g. proline causes a kink), other components (e.g. iron) and disulfide bridges.
• Quaternary Structure
  • Various polypeptides join together with intermolecular forces to form a protein

Denaturing of Proteins

• Change in è Heat, pH, temperature, ionic concentration etc.
  • Can cause changes in the 3-D structure of the protein

                        Change can be permanent if the 1° structure is broken

                        Change can be reversed if only the 3° structure is broken

• Use of denaturing proteins à Food preservation