In the primary structure of a protein

A. The left end represents first amino acid

B. The right end represents last amino acid

C. The left end represents last amino acid

D. The right end represents first amino acids

Choose the correct option.

Solution:

The primary structure of a protein refers to the linear sequence of amino acids in a polypeptide chain. By convention, the polypeptide chain is written from the amino-terminal (N-terminal) end to the carboxyl-terminal (C-terminal) end. The N-terminal end, which has a free amino group, is considered the left end and represents the first amino acid. The C-terminal end, which has a free carboxyl group, is considered the right end and represents the last amino acid. Therefore, statements A and B are correct.