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. Secondary structures, which include the alpha helix or beta pleated sheet, are held together by interactions between R groups.

C. Tertiary structure is the overall shape of a polypeptide, which may be stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and peptide bonds.

D. Quaternary structure is only found in proteins that have four identical polypeptide subunits.

The right answer is 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.

Explanation:

Proteins are aminoacids's polymers. There are 20 different aminoacids that differs only in their R groups. There are four kind of protein structures:

1) Primary structure: it refers to tha secuence of aminoacids in the protein and is defined by DNA.

2) Secondary structure: it describes the situation in which we can identify repeated segments along the polypeptid chain. There are two secondary structures: alpha helix and beta pleated. This two conformation are held together by interactions between peptidic groups. R groups can interact only if they are small.

3) Tertiary structure: is the three-dimentional conformation of the polypeptid and it is stabilized by hydrogen bonds, electrostatic interactions, hydrophobic interactions and disulphide bonds. Stabilizing bonds can be between peptidic groups (peptide bond).

4) Quaternary structure: it applies for that proteins conformed by different subunits. It describes the conformation and interaction between these subunits in the polypeptid.