1. The amino acids are linked covalently by peptide bonds.
2. The carbonyl group of the first amino acid react with the amino group of the second amino acid to give an amide linkage (- CONH) between these aminoacids.
This amide linkage is called peptide bond.

3. The resulting compound is called a dipeptide. Because, two amino acids are inovived for getting one peptide bond.
4. If large number of amino acids combined through peptide bond, the resulting giant molecule is called a protein.
5. The amino end of the peptide is known as Nterminal, while the carboxy end is called C – terminal.