The primary structure of a protein molecule has
a. Two ends
b. One end
c. Three ends
d. No ends
The primary structure of a protein has a linear sequence of amino acids in a polypeptide chain which is held together by peptide bonds. These are two ends of a polypeptide chain, the carboxyl terminus (C-terminus) and the amino terminus (N-terminus) based on the nature of the free group on each other extremities. Hence, Option (a) is the correct answer.