Final answer:
The primary, secondary, tertiary, and quaternary structures of a protein determine its function, with the tertiary structure being most closely associated with function. Changes in any structural level can affect protein activity.
Step-by-step explanation:
Protein Structure and Function
The combination of primary, secondary, tertiary, and quaternary levels of protein structure is responsible for determining the function of a protein. The primary structure consists of the sequence of amino acids, dictating the subsequent levels of structure. The secondary structure refers to local folding into patterns like α-helices and β-pleated sheets due to hydrogen bonding. The tertiary structure is the three-dimensional folding pattern due to interactions between side chains, such as hydrophobic interactions, ionic bonds, and disulfide bridges. Lastly, the quaternary structure occurs when multiple polypeptide chains come together to form a functional unit.
The function of a protein is most often associated with its tertiary structure, as this is where the intricate folding creates a unique three-dimensional shape necessary for its specific functions. However, alterations in any level of structure from primary to quaternary can lead to changes in the protein's functionality or even cause it to become non-functional, which is what happens in denaturation.