When end-group analysis was done on the protein insulin, the results indicated that both glycine and phenylalanine were N-terminal amino acids and both asparagine and alanine were C-terminal amino acids. These results indicate that
A) the experiment was done incorrectly
B) no conclusions can be drawn
C) there were impurities in the sample
D) insulin consists of two polypeptide chains

Question

Quizplus · Accepted Answer

The presence of two N-terminal amino acids (glycine and phenylalanine) and two C-terminal amino acids (asparagine and alanine) in insulin suggests that it is composed of two polypeptide chains, each with its own N- and C-termini.

When End-Group Analysis Was Done on the Protein Insulin, the Results