Question

Which of the four levels of structure of a protein determines the condensed 3-D shape of the molecule and determines its function?

1) Primary structure
2) Secondary structure
3) Tertiary structure
4) Quaternary structure

Answer 1

The tertiary structure of a protein is responsible for its 3-D shape and function, involving the overall folding pattern of the polypeptide chain into a compact, globular form.

Step-by-step explanation:

The level of protein structure that determines the condensed 3-D shape of the molecule and thus its function is the tertiary structure. The primary structure of a protein is the sequence of amino acids. The secondary structure involves configurations like helices and sheets, which are local folding patterns. However, it is the tertiary structure that gives a protein its overall three-dimensional shape by folding the polypeptide chain into a compact, globular form, which is crucial for the protein's biological function.

Furthermore, if a protein is made up of more than one polypeptide chain, the arrangement of these separate chains is referred to as the quaternary structure. Various types of bonding such as ionic bonds, hydrogen bonds, disulfide linkages, and dispersion forces maintain the protein's shape. Incorrect folding or denaturation can disrupt the tertiary structure, often leading to loss of function.