Q.66 Chloramphenicol and tetracycline are broad spectrum antibiotics which inhibit bacterial
growth by targeting _________.
(A) cell wall synthesis (B) protein synthesis
(C) RNA synthesis (D) DNA synthesis
Chloramphenicol and tetracycline, broad-spectrum antibiotics, inhibit bacterial growth by targeting protein synthesis. This is the correct answer for the multiple-choice question.
Option Analysis
(A) Cell wall synthesis: Incorrect. Antibiotics like beta-lactams (penicillin) and glycopeptides (vancomycin) target peptidoglycan formation in bacterial cell walls. Chloramphenicol and tetracycline do not interfere with this process.
(B) Protein synthesis: Correct. Both bind to bacterial ribosomes—chloramphenicol to the 50S subunit blocking peptidyl transferase, and tetracycline to the 30S subunit preventing tRNA binding—halting translation.
(C) RNA synthesis: Incorrect. Rifampin and rifamycins inhibit bacterial RNA polymerase, blocking transcription initiation.
(D) DNA synthesis: Incorrect. Quinolones (ciprofloxacin) and fluoroquinolones target DNA gyrase and topoisomerase IV, disrupting replication.
Chloramphenicol and tetracycline broad spectrum antibiotics protein synthesis inhibitors play a key role in combating bacterial infections by targeting essential cellular processes. These drugs are vital in microbiology and pharmacology studies, especially for exams like CSIR NET Life Sciences.
Mechanism of Action
Chloramphenicol binds reversibly to the 50S ribosomal subunit, inhibiting peptidyl transferase and preventing peptide bond formation during translation. Tetracycline attaches to the 30S subunit, blocking aminoacyl-tRNA entry to the A-site and halting protein chain elongation. Both actions make bacteria unable to produce proteins needed for growth and survival.
Spectrum and Clinical Use
These broad spectrum antibiotics act against Gram-positive, Gram-negative, and some anaerobic bacteria. Chloramphenicol treats severe infections like typhoid and meningitis, while tetracycline addresses respiratory, skin, and rickettsial diseases. Their bacteriostatic nature suits non-critical cases, though resistance limits routine use.
Comparison with Other Targets
| Target | Examples | Mechanism |
|---|---|---|
| Cell Wall | Penicillin, Vancomycin | Block peptidoglycan cross-linking |
| Protein Synthesis | Chloramphenicol, Tetracycline | Inhibit ribosomal translation |
| RNA Synthesis | Rifampin | Block RNA polymerase |
| DNA Synthesis | Ciprofloxacin | Inhibit gyrase/topoisomerase |
This table highlights why chloramphenicol and tetracycline specifically target protein synthesis, distinguishing them in antibiotic classification.
