amino acid molecules that contain: 1. an amino group (-NH2) 2. carboxyl group (-COOH) 3. R group/side chain - determines the chemical properties 4. Hydrogen atom (-H) main focus is on alpha aa's - not every amino acid is an alpha aa (GABA) - not every amino acid is coded for a codon - some aa's are converted to non codon coded aa for specific reasons - in eukaryotes they are all L configuration alpha amino acid aa that the amino group and the carboxyl group are attached to the same carbon (alpha carbon of the carboxylic acid) alpha carbon is chiral (beisdes glycine) - optically active - in eukaryotes they are all L configuration R group side group of the amino acid every amino acid has a different one determines the properties of the amino acids and thus their functions GABA gamma aminobutyric acid amino group and carboxyl group are not on the same carbon amino group is on the gamma carbon from the carbonyl proteinogenic amino acids 20 alpha amino acids amino acids that are encoded by the human genetic code through codons since they are all chiral at the alpha carbon (besides glycine) - L CONFIGURATION have at least two group that can be protonated/deprotonated - two (maybe three) pka's chiral amino acids the alpha carbon in alpha aa's optically active has four different groups attached to it exception - glycine (has two H's) L configuration - goes to the S absolute configuration G Glycine GLY R group - H ACHIRAL (not L or D) smallest amino acid nonpolar, non-aromatic R group hydrophobic - interior of proteins Cahn Ingold Prelog System L amino acids are S configuration AMINO GROUP IS TO THE LEFT in a fisher projection C Cysteine CYS R group = -CH2SH polar side chain has a thiol group -since sulfur is larger and less electronegative than oxygen SH bond is weaker than an OH bon -makes SH prone to OXIDATION reaction L amino acid R absolute configuration A Alanine ALA R Group = -CH3 nonpolar, non-aromatic R group alkyl side chain with one carbon makes it nonpolar L amino acid S absolute Configuration hydrophobic - interior of proteins R Arginine ARG R group = -CH2CH2CH2-NH-C(=NH)NH2 positive/basic Side Chain -three nitrogens in its side chain positive charge is delocalized over all three nitrogen atoms L amino acid S absolute Configuration hydrophilic - surface of proteins N Asparagine ASN R group = -CH2C(O)NH2 polar side chain amide side chain L amino acid S absolute Configuration hydrophilic - surface of proteins 00:0201:08 D Aspartic Acid/ ASPARTATE ASP R group = -CH2C(O)OH Negative/Acidic Side Chain L amino acid S absolute Configuration hydrophilic - surface of proteins