Which of the following statements is an accurate description of proteins? Which of the following statements is an accurate description of proteins?
A. The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene.
B. The 20 amino acids found in proteins differ in the composition of their R groups, which may be either polar or charged.
C. Secondary structures, which include the alpha helix or beta pleated sheet, are held together by interactions between R groups.
D. Tertiary structure is the overall shape of a polypeptide, which may be stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and peptide bonds.
E. Quaternary structure is only found in proteins that have four identical polypeptide subunits.

The primary structure is the main chain of protein formed by the binding of amino acids and showing the sequence in which they appear is called the primary structure of the protein. In other words, the primary structure of a protein is the order of amino acids in a polypeptide, as encoded in the DNA of a gene.

However, the same protein can also acquire secondary, tertiary and even quaternary structures. This occurs as a result of intermolecular interactions between parts of the same protein or between several protein chains.

A protein has at least 50 amino acids, and in the primary structure, they are in the order indicated by DNA.