Lecture Three
Amino acids & PeptidesDr. Khalidah Merzah
Amino acids and peptides
Properties of Amino Acids• Capacity to polymerize
• Novel acid-base properties
• varied structure and chemical functionality
• Chirality
•Steroisomers / enantiomers
•Biological system only synthesize and use L-aminoacids
Essential/Non-Essential Amino Acids
• Essential –histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine• Non-essential – alanine, arginine*, aspartate, asparagine, cysteine*, glutamate, glutamine, glycine*, proline*, serine, tyrosine*
Protein Nomenclature
• Peptides 2 – 50 amino acids• Proteins >50 amino acids
• Amino acid with free α-amino group is the amino-terminal or N-terminal residue
• Amino acid with free α-carboxyl group is the carboxyl-terminal or C-terminal residue
• Three letter code – Met-Gly-Glu-Thr-Arg-His
• Single letter code – M-G-E-T-R-H
