Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 6

An Antibiotic Inhibitor of Translation. Puromycin is a powerful inhibitor of protein synthesis (see page 697). It is an analog of the 3 end of aminoacyl tRNA, as Figure 22-21 reveals. (R represents the functional group of the amino acid;
R represents the remainder of the tRNA molecule.)When puromycin is added to a cell-free system containing all the necessary machinery for protein synthesis, incomplete polypeptide chains are released from the ribosomes. Each such chain has puromycin covalently attached to one end.
(a)Explain these results.
(b)To which end of the polypeptide chains would you expect the puromycin to be attached Explain.
(c)Would you expect puromycin to bind to the A or P site on the ribosome or to both Explain.
(d)Assuming that it can penetrate into the cell equally well in both cases, would you expect puromycin to be a better inhibitor of protein synthesis in eukaryotes or bacteria Explain.