Question

some proteins are made of only one polypeptide. but proteins with more than one polypeptide chain have an additional level of organization. in these proteins, tertiary structures will associate with one another to form a quaternary structure. the model below shows the four levels of organization of a protein with multiple polypeptide chains. select the true statements. quaternary structures have multiple polypeptide chains. the tertiary structure is the final shape of a protein with more than one polypeptide chain. tertiary structures associate to form a quaternary structure. all proteins have a quaternary structure.

Explanation:

• Quaternary structures are formed by the association of multiple polypeptide chains (as stated in the text: "proteins with more than one polypeptide chain... tertiary structures will associate with one another to form a quaternary structure").
• The text clearly says that for proteins with more than one polypeptide chain, tertiary structures associate to form quaternary structure, so the final shape is quaternary (not tertiary) for such multi - chain proteins.
• As per the text, "tertiary structures will associate with one another to form a quaternary structure".
• The first sentence of the text says "Some proteins are made of only one polypeptide", so not all proteins have a quaternary structure.

Answer:

• Quaternary structures have multiple polypeptide chains.
• Tertiary structures associate to form a quaternary structure.