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': 'Enzymes are usually: \nSelect and explain. \nA. Lipid, B. Nucleic acids, C. Carbohydrates, D. Protein', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Enzymes are mainly proteins, that catalyze (i.e., increase the rates of) chemical reactions with the exception of catalytic RNA molecules, or ribozymes.In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme conves them into different molecules, called the products.', 'role': 'assistant'}]