Antibiotics/Chemical Control Agents (Lecture 9)

Question 1

What does sulfamethoxazole do?

Answer 1

• Inhibits folic acid synthesis
• Broad spectrum

** Competitively inhibits the synthesis of dihydrofolic acid from PABA.**

** sulfa drugs are selectively toxic due to competitive inhibition of folic acid synthesis enzymes **

Question 2

What does trimethoprim do?

Answer 2

• Inhibits folic acid production
• Broad spectrum

** competitively inhibits the synthesis of tetrahydrofolic acid **

** combined with sulfa drugs to increase efficacy of treatment **

Question 3

What does chloramphenicol do?

Answer 3

• Binds to 23s rRNA on 50S ribosomal subunit
• Inhibits peptidyl transferase reaction (inhibits fromation of peptide bond)

** NOTE: 23s forms peptide bond during translation **

Question 4

What does tetracycline do?

Answer 4

• Combines with 30S ribosomal subunit
• Inhibits binding of aminoacyl-tRNA molecules to the A site of the ribosome
  
  • (new amino acid can not be brought into growing peptide chain)
• Broad spectrum
• Bacteriostatic

Question 5

What does vancomycin do?

Answer 5

• Inhibits cell wall synthesis

Question 6

What does cephalosporins do?

Answer 6

• Distrupt synthesis of the peptidoglycan layer froming the cell wall
• Bactericidal
• Broad Spectrum
• Beta-lactam antibiotic

Question 7

What does penicillin do?

Answer 7

• Blocks enzyme that catalyzes transpeptidation (formation of cross-links in peptidoglycan)
• Prevents synthesis of complete cell walls leading to lysis of cell
• Acts only on growing bacteria that are synthesizing new peptidoglycan

Question 8

What does erythromycin do?

Answer 8

• Binds to 23S rRNA of 50S ribosomal subunit
• Inhibits peptide chain elongation
• Broad spectrum
• Usually bacteriostatic

Question 9

What does streptomycin do?

Answer 9

• Changes shape of 30S portion, causing code on mRNA to be read incorrectly.