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. all proteins have a quaternary structure. tertiary structures associate to form a quaternary structure. the tertiary structure is the final shape of a protein with more than one polypeptide chain.

Explanation:

1. For "Quaternary structures have multiple polypeptide chains": The text states "proteins with more than one polypeptide chain... tertiary structures will associate with one another to form a quaternary structure", so quaternary structures involve multiple polypeptide chains (from associated tertiary structures of different chains), so this is true.
2. For "All proteins have a quaternary structure": The text says "Some proteins are made of only one polypeptide" and quaternary structure is for proteins with more than one polypeptide chain, so not all proteins have quaternary structure, so this is false (should not be selected).
3. For "Tertiary structures associate to form a quaternary structure": The text directly says "tertiary structures will associate with one another to form a quaternary structure", so this is true.
4. For "The tertiary structure is the final shape of a protein with more than one polypeptide chain": For proteins with multiple polypeptide chains, the final shape (after association of tertiary structures) is quaternary structure, so tertiary is not the final shape for such proteins, so this is false (should not be selected).

Answer:

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