Final answer:
The N-terminus of a polypeptide is characterized by a free amino group, indicating the start point of protein synthesis and the sequential addition of amino acids. The N-terminal end is crucial for protein composition analysis and is represented first in the written structure of proteins.
Step-by-step explanation:
The term N-terminus refers to the presence of a free amino group at the beginning of a polypeptide chain. This end is where the protein synthesis starts, adding amino acids one by one to the C-terminus. The N-terminal amino acid is the one whose amino group is not involved in forming a peptide bond, symbolizing the start of the protein structure. The detection and analysis of the N-terminal amino acid are critical in studying protein composition, which is often done using reagents like Sanger's reagent, Edmann's reagent, or Dansyl chloride. It is important to note that the representation of proteins on paper typically begins with the N-terminal amino acid on the left, progressing to the C-terminal amino acid on the right.