Q.Write the names and schematic representations of all the possible dipeptides formed from alanine, glycine and tyrosine.

Two amino acids condense, losing water, to form an amide (peptide) bond linking them.

A peptide (amide) linkage is formed by the condensation reaction between the carboxyl group (–COOH) of one amino acid and the amino group (–NH₂) of another amino acid, with elimination of a water molecule:

$H_2N-CH_2-COOH\ (glycine) + H_2N-CH(CH_3)-COOH\ (alanine) \rightarrow H_2N-CH_2-CO-NH-CH(CH_3)-COOH + H_2O$ …

Amino acids condense, losing water, to form an amide (peptide) linkage between the $-COOH$ of one and the $-NH_2$ of the next.

Amino acids are organic compounds that contain both a basic amino group ($-NH_2$) and an acidic carboxyl group ($-COOH$) attached to the same carbon skeleton (typically both on the $\alpha$-carbon, giving $\alpha$-amino acids). They are the building-block monomers from which proteins are constructed.

Peptide bond formation: when the carboxyl group of one amino acid reacts with the amino group of a second amino acid, a molecule of water is eliminated and an amide linkage — called a peptide bond ($-CO-NH-$) — is formed between them:

$H_2N-CHR_1-COOH + H_2N-CHR_2-COOH \rightarrow H_2N-CHR_1-CO-NH-CHR_2-COOH + H_2O$

…