This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Proteins are linear polymers of amino acids. They fold into compact structures. Sometimes, these folded structures associate to form homo-or hetero-dimers. Which one of the following refers to this associated form? \nSelect and explain. \nA. Denatured state, B. Molecular aggregation, C. Precipitation, D. Quaternary structure', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Some proteins consist of two or more polypeptide chain, called subunits (protomer).\nThe spatial relation of subunits with one another is called the quaternary structure.\nDimers contain two polypeptide chains. Homodimers have same polypeptide chains whereas heterodimers have different polypeptide chains.', 'role': 'assistant'}]