This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure & Function of Protein, Subject name: Biochemistry
[{'content': 'The portion of the antigen molecule which is recognized by antibody is known as: \nSelect and explain. \nA. Hapten, B. Epitope, C. Complement, D. Variable region', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. EpitopeEpitope is a localized region on the surface of an antigen that is capable of eliciting an immune response and of combining with a specific antibody to counter that response. Hapten is a small molecule that reacts with a specific antibody but cannot induce the formation of antibodies unless bound to a carrier protein or other large antigenic molecule. A complement is a complex system of proteins found in normal blood plasma that combines with antibodies to destroy pathogenic bacteria and other foreign cells. Also called alexin. A variable region is present in the antibody that shows many sequence differences between antibodies of different specificities; the part of the antibody that binds to the antigen.', 'role': 'assistant'}]