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: Unknown
[{'content': 'In Immune complex formation, which structure of a protein is involved? \nSelect and explain. \nA. Primary, B. Secondary, C. Tertiary, D. Quaternary', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The modular nature of protein synthesis and folding are embodied in the concept of orders of protein structure.\nPrimary structure is the sequence of the amino acids in a polypeptide chain.\nSecondary structure is the folding of short (3- to 30-residue), contiguous segments of polypeptide into geometrically ordered units.\nTertiary structure is the assembly of secondary structural units into larger functional units such as the mature polypeptide and its component domains.\nQuarternary structure is the number and types of polypeptide units of oligomeric proteins and their spatial arrangement.\nIn some cases, the proteins are assembled from more than one polypeptide or protomer.\nQuarternary structure defines the polypeptide composition of a protein, and for an oligomeric protein, the spatial relationships between its subunits or protomers.\nMonomeric proteins consist of a single polypeptide chain, and are hence, devoid of a quarternary structure.\nDimeric proteins consist of two polypeptide chains.\nHomodimers contain two copies of the same polypeptide chain, while in heterodimers, the polypeptides differ.\nRef: Harper’s ‘Illustrated Biochemistry’; 27/e, pg 30, 34', 'role': 'assistant'}]