The number of peptide bonds in a polypeptide chain composed of ‘n’ number of amino acids will be ‘n-1’.
Two amino acids join together by forming a single peptide bond. These two amino acids can bond to a third amino acid by forming a second peptide bond. Thus, we see that the number of peptide bonds in a single polypeptide chain will always be one less than the total number of amino acids.
For a polypeptide containing 25 amino acids, the number of polypeptide bonds will be 24.