This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Antimicrobial Drugs, Subject name: Pharmacology
[{'content': 'The mechanism of action of tetracyclines involves: \nSelect and explain. \nA. Binding of a component of the 50S ribosomal subunits, B. Inhibition of translocase activity, C. Blockade of binding of aminoacyl-tRNA to bacterial ribosomes by binding to 30S ribosome, D. Selective inhibition of ribosomal peptidyl transferase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: - Chloramphenicol acts by inhibiting peptide bond formation. - Tetracyclines act by binding to 30S ribosome and inhibiting the binding of acyl tRNA to A site of mRNA-ribosome complex. - It enters bacteria by forming pores in the cell membrane and by active transpo which pumps it across the cell membrane. - Macrolides, Clindamycin and Quinpristine act by inhibiting translocation.', 'role': 'assistant'}]