Peptide: A compound consisting of two or more amino acids linked by peptide bonds. (This term is rarely used, and it is generally discussed directly about peptide chains or polypeptides. )

Peptide bond: chemical reaction can occur between amino acids, which is called dehydration condensation. A special chemical bond (CO-NH), i.e. peptide bond, is formed at the place where water is removed. The pictures in the specific process reference book are very clear. These pictures must be completely understood.

Peptide chain: a chain structure formed by dehydration and condensation of two or more amino acids, also known as polypeptide.

Polypeptide: This is very simple. Just count the number of amino acids in the peptide chain.

Calculation of peptide bonds: number of peptide bonds = number of amino acids-number of peptide chains.