MCQ 01-10 – PHARMACOLOGY

1. Which of the following is a broad-spectrum antibiotic?
   A. Penicillin G
   B. Amoxicillin
   C. Erythromycin
   D. Chloramphenicol

✅ Answer: D. Chloramphenicol
💡 Explanation: Chloramphenicol acts on both Gram-positive and Gram-negative bacteria.

2. The mechanism of action of penicillin is:
   A. Inhibition of protein synthesis
   B. Inhibition of nucleic acid synthesis
   C. Inhibition of cell wall synthesis
   D. Disruption of cell membrane

✅ Answer: C. Inhibition of cell wall synthesis
💡 Explanation: Penicillin inhibits peptidoglycan synthesis in bacterial cell walls.

3. Tetracyclines act by inhibiting:
   A. RNA polymerase
   B. 30S ribosomal subunit
   C. 50S ribosomal subunit
   D. DNA gyrase

✅ Answer: B. 30S ribosomal subunit
💡 Explanation: Tetracyclines block aminoacyl-tRNA binding to the ribosome, preventing protein synthesis.

4. Which of the following antibiotics is ototoxic and nephrotoxic?
   A. Streptomycin
   B. Ampicillin
   C. Azithromycin
   D. Chloramphenicol

✅ Answer: A. Streptomycin
💡 Explanation: Streptomycin (an aminoglycoside) can damage the ear (ototoxicity) and kidneys (nephrotoxicity).

5. Vancomycin is mainly used against:
   A. Gram-negative bacteria
   B. Gram-positive bacteria
   C. Fungi
   D. Viruses

✅ Answer: B. Gram-positive bacteria
💡 Explanation: Vancomycin is effective against resistant Gram-positive organisms like MRSA.

6. Which antibiotic inhibits DNA gyrase?
   A. Erythromycin
   B. Ciprofloxacin
   C. Doxycycline
   D. Linezolid

✅ Answer: B. Ciprofloxacin
💡 Explanation: Fluoroquinolones like ciprofloxacin inhibit bacterial DNA gyrase and topoisomerase IV.

7. Sulfonamides act by inhibiting:
   A. Folic acid synthesis
   B. Cell wall synthesis
   C. Protein synthesis
   D. DNA replication

✅ Answer: A. Folic acid synthesis
💡 Explanation: Sulfonamides are structural analogs of PABA and inhibit dihydropteroate synthase.

8. Which antibiotic causes gray baby syndrome?
   A. Gentamicin
   B. Chloramphenicol
   C. Tetracycline
   D. Erythromycin

✅ Answer: B. Chloramphenicol
💡 Explanation: Due to immature liver enzymes in neonates, chloramphenicol accumulates and causes toxicity.

9. The antibiotic erythromycin belongs to which class?
   A. Aminoglycoside
   B. Macrolide
   C. Beta-lactam
   D. Quinolone

✅ Answer: B. Macrolide
💡 Explanation: Erythromycin is a macrolide that inhibits protein synthesis by binding to the 50S ribosomal subunit.

10. Metronidazole is mainly effective against:
    A. Gram-positive bacteria
    B. Gram-negative bacteria
    C. Anaerobic bacteria and protozoa
    D. Viruses

✅ Answer: C. Anaerobic bacteria and protozoa
💡 Explanation: Metronidazole damages DNA of anaerobic organisms and protozoa like Giardia and Entamoeba.