This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
[{'content': "Fischer's lock and key theory' postulates that: \nSelect and explain. \nA. Active site in enzyme exists in proper conformation to the substrate molecule even in absence of substrate, B. Active site during binding to substrate under goes conformational changes to fit, C. There is absolute specificity in reaction between enzyme and substrate, D. Enzymes have catalytic power and accelerate reaction by reducing energy of activation", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A. Active site in enzyme exists in proper conformation to the substrate molecule even in absence of substratea. Fischer's lock and key theory for action of enzymes is also called rigid template model.b. The Fischer's lock and key theory explains the specificity of enzyme substrate interactions-c. The Fischer's model fails to explain the dynamic changes in the structure of enzyme that are required for catalysis.d. These are explained by the induced fit model given by Koshland.", 'role': 'assistant'}]