: 200
Essential amino acids (PVT TIM HALL): Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine. 10 total; His and Arg are essential for children only (8 for adults). All natural amino acids are L-configuration. Glycine is the only achiral amino acid (R=H). Peptide bond properties: partial double bond (C-N 1.33 Angstrom), planar, trans preferred, restricted rotation. n amino acids → n-1 peptide bonds. Amino acids as acids and bases: at physiological pH, exist as zwitterions (NH3+, COO-). High melting points (ionic character). Soluble in water, insoluble in organic solvents. Classification by side chain: nonpolar (Gly, Ala, Val, Leu, Ile, Pro, Phe, Trp, Met), polar uncharged (Ser, Thr, Cys, Tyr, Asn, Gln), positively charged/basic (Lys, Arg, His), negatively charged/acidic (Asp, Glu). Amino acid synthesis: Strecker (RCHO + NH3 + HCN → hydrolysis), Gabriel phthalimide method. Detection: ninhydrin (blue-violet; proline → yellow).