8. Some antibiotics work by preventing protein synthesis in bacteria by binding to their ribosomes. Which statement explains why these antibiotics kill bacterial cells but not human cells? A. Antibiotics recognize human genes but not bacterial genes B. Ribosomes in human cells have a different structure to those in bacterial cells C. mRNA in bacterial cells is not processed before translation D. Both DNA and ribosomes are located in the cytoplasm in bacteria E. Ribosome in human cells is located inside the nucleus 9. Shine Dalgarno sequence is A. an RNA component of ribosome B. a promoter sequence C. a sequence for initiator tRNA binding D. located upstream of the coding sequence E. a sequence for recognition by RNA polymerase holoenzyme 10. Which of the following statements about ribosome is INCORRECT? A. Ribosome consists of protein and RNA B. 50S subunit can't bind to 30S subunit till IF1 an IF3 dissociate from 30S subunit C. Energy is consumed when ribosome moves along the mRNA in elongation D. Releasing factors bind to the A site on the ribosome E. Ribosome moves forward on the mRNA from 3' to 5' direction
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Erythromycin: acts by inhibition of protein synthesis by binding to the 23S ribosomal RNA molecule in the 50S subunit of ribosomes in susceptible bacterial organisms. Penicillin: kills bacteria by binding the beta-lactam ring to DD-transpeptidase, inhibiting its cross-linking activity and preventing the formation of new cell walls. A bacterial cell without a cell wall is vulnerable to outside water and molecular pressures, causing the cell to die quickly. Kanamycin: Kanamycin works by binding to the bacterial 30S ribosomal subunit, causing mRNA misreading and preventing the bacterium from synthesizing proteins required for growth. Chloramphenicol: Chloramphenicol is an antibacterial with broad activity against gram-positive, gram-negative, and Rickettsia bacteria. It works by interfering with bacterial protein synthesis by binding to ribosomes. Novobiocin: inhibition of the GyrB subunit of the bacterial DNA gyrase enzyme, which is involved in energy transfer. Tetracycline: binds reversibly to the 30S ribosomal subunit in a position that prevents aminoacyl-tRNA from binding to the acceptor site on the mRNA-ribosome complex. Streptomycin: interferes with the function of ribosomes in bacterial cells, the complex molecular machines that create proteins by linking amino acids together. Neomycin: Through irreversible binding to the 30S ribosomal subunit of susceptible bacteria, it inhibits bacterial protein synthesis. Question: Which antibiotics seem to have the broadest spectrum of activity and why?
Adi S.
The discovery of the antibiotic Penicillin in the 1920s made a big impact on human history. Not only did it provide a cure for bacterial infections that were once deadly, but it also led to a golden age in discovery of new antibiotics. The great benefit of these drugs is that antibiotics inhibit the growth of bacterial cells or kill them outright, and yet, on the whole, do not harm eukaryotic cells. Answer BOTH of the following questions: Given the following list of antibiotics Penicillin Blocks cell wall synthesis Tetracycline Blocks protein synthesis by binding to the 30S Unit of the ribosome Chloramphenicol Blocks protein synthesis by binding to the 50S Unit of the ribosome Sulfonamides Inhibit folic acid synthesis Vancomycin and their targets, explain how each stops bacteria without harming human cells. Base your analyses on the differences between eukaryotic and prokaryotic cells. Considering the targets of these antibiotics, explain why antibiotics in general would not be useful for treating a viral infection.
Madhur L.
Figure 15.16 Many antibiotics inhibit bacterial protein synthesis. For example, tetracycline blocks the A site on the bacterial ribosome, and chloramphenicol blocks peptidyl transfer. What specific effect would you expect each of these antibiotics to have on protein synthesis? Tetracycline would directly affect: a. tRNA binding to the ribosome b. ribosome assembly c. growth of the protein chain Chloramphenicol would directly affect a. tRNA binding to the ribosome b. ribosome assembly c. growth of the protein chain
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