MCQ on Mode of Action of Antibiotics
1. Penicillin causes bacterial cell lyses by inhibiting the enzyme that catalyzes cross- linking of peptidoglycan chains of the bacterial cell wall. The enzyme is
a) enolpyruvyl transferase
b) transglycolase
c) transpeptidase
d) ribonuclease
2. Which of the following antibiotics blocks the first step of
peptidoglycan cell wall synthesis by inhibiting
enzyme MurA?
a) Fosfomycin
b) Penicillin
c)
Vancomycin
d) Bacitracin
3. Which of the following is a DNA gyrase inhibitor, thus
disrupting bacterial DNA replication?
a) ciprofloxacin
b) Vancomycin
c) Chloramphenicol
d)
Streptomycin
4. All the following drugs are bacterial cell wall synthesis
inhibitors except
a)Vancomycin
b) Bacitracin
c) Fosfomycin
d) Rifamycin
5. All the following are protein synthesis inhibitors which binds
to the 50S ribosomal subunit and blocks protein synthesis except
a) Streptomycin
b) Erythromycin
c) Cliindamycin
d) Chloramphenicol
6. Which of the following antibiotic inhibits transcription by binding
DNA at the transcription initiation complex and preventing elongation of RNA
chain by RNA polymerase?
a)Rifampicin
b) Streptomycin
c) Carbenicillin
d) Actinomycin
D
7. This antibiotic binds to the D-ala residues preventing cross
linking of cell wall strands by preventing the binding of cross linking enzyme.
The antibiotic is
a) Erythromycin
b) Vancomycin
c) Cephalosporin
d)Chloramphenicol
8. Which of the following is not a protein synthesis inhibitor by
binding to 30 S small ribosomal subunit?
a) Kanamycin
b) Streptomycin
c) Erythromycin
d)Tetracycline
9. Which of the following antibiotic prevents bacterial
transcription by directly binding to the bacterial RNA polymerase?
a) Rifampin
b) polymixin
c) Puromycin
d)
Streptomycin
10. The antibiotic that prevents peptidoglycan synthesis by
blocking the transport of peptidoglycan monomer is
a)Cephamycin
b) Cephalosporin
c) Bacitracin
d)Vancomycin
11. Cephalosporin controls bacterial growth by inhibiting _________ synthesis.
a)DNA b) Cell wall c) Plasma membrane d)Capsule
12. Name the antibiotic produced by Streptomyces orientalis.
a) Cephalosporins
b) Cycloserine
c) Bacitracin
d) Vancomycin
13.The antibiotic streptomycin was isolated from
a) Streptomyces griseus
b) Streptomyces venezuele
c) Streptomyces aureofaciens
d) Streptomyces rimosus
14. Mycoplasma are resistant to common antibiotics like penicillin because of
a) Sterols in the membrane
b) Lack of cell wall
c) Small genome size
d) Active repairing mechanism
15. Match Group I with Group II
Group I Group II
a) Nalidixic acid 1. RNA polymerase
b) Tetracycline 2. DNA gyrase
c) Erythromycin 3. DNA polymerase
d) Rifampin 4. 50S ribosomal submit
5. Aminoacyl tRNA
A) a-3, b-4, c-5, d-1
B) a-5, b-1, c-4, d-2
C) a-2, b-5, c-4, d-1
D) a-2, b-5, c-1, d-4
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Answers
1. c) transpeptidase
2. a) Fosfomycin
3. a) ciprofloxacin
4. d) Rifamycin
5. a) Streptomycin
6. d) Actinomycin D
7. b) Vancomycin
8. c) Erythromycin
9. a) Rifampin
10. c) Bacitracin
11. b) Cell wall
12. d) Vancomycin
13. a) Streptomyces griseus
14. b) Lack of cell wall
15. C) a-2, b-5, c-4, d-1
