Amino Acid Structure and Peptide Formation

Amino Acids Classification

• Dicarboxylic amino acids: Aspartic acid (Asp, D) and Glutamic acid (Glu, E)
• Amino acids with amide group: Asparagine (Asn, N) and Glutamine (Gln, Q)
• Dibasic amino acids: Lysine (Lys, K) and Arginine (Arg, R)
• Heterocyclic amino acid: Histidine (His, H)
• Imino acid: Proline (Pro, P) - also known as Imino acid due to its Pyrrolidine ring structure

Aromatic Amino Acids

• Phenylalanine (Phe, F)
• Tyrosine (Tyr, Y)
• Tryptophan (Try, W)

Structure of Amino Acids

• Each amino acid has a core structure consisting of a central carbon atom known as the alpha (α) carbon
• Amino acids contain an amino group, a carboxylic group, and a side chain

Formation of Peptide Linkage

• Dipeptide: 2 amino acids linked together
• Tripeptide: 3 amino acids linked together - can have 20^3 = 8000 different combinations
• Tetrapeptide: 4 amino acids linked together
• Oligopeptide: 5-9 amino acids linked together
• Polypeptide: 10-50 amino acids linked together
• Polypeptides with more than 50 amino acids are usually termed as proteins

Simple and Branched-Chain Amino Acids

• Simple amino acids: Glycine (Gly, G), Alanine (Ala, A)
• Branched-chain amino acids: Valine (Val, V), Leucine (Leu, L), Isoleucine (Ile, I)

Hydroxy and Sulfur-Containing Amino Acids

• Hydroxy amino acids: Serine (Ser, S), Threonine (Thr, T)
• Sulfur-containing amino acids: Cysteine (Cys, C), Methionine (Met, M)

Learn about the core structure of amino acids, including the alpha carbon, amino group, carboxylic group, and side chain. Understand how peptide linkages are formed and the differences between dipeptides and tripeptides.