Question

During the elongation phase of protein synthesis, a second antibiotic inhibitor blocks protein synthesis at the translocation reaction. At the inhibited ribosome, the P site is occupied by

a. aminoacyl tRNA.
b. empty tRNA
c. peptidyl tRNA
d. nothing

Answer 1

The P site of a ribosome inhibited during the elongation phase of protein synthesis would be occupied by peptidyl tRNA, as this occupation is part of the normal process of translocation which is blocked by certain antibiotics, leading to inhibited protein synthesis.

Step-by-step explanation:

During the elongation phase of protein synthesis, if a second antibiotic inhibitor blocks protein synthesis at the translocation reaction, then the P-site of the inhibited ribosome would be occupied by peptidyl tRNA. This reaction is necessary for the growth of the protein chain, allowing tRNAs to shift from the A site to the P site, and then to the E site, as they bring in new amino acids to form peptide bonds and elongate the polypeptide chain. The action of translocation is powered by GTP hydrolysis and is facilitated by elongation factors. During this phase, the P-site tRNA, which is linked to the growing polypeptide chain, needs to move to the E site to make room for the next incoming aminoacyl tRNA at the A site. An antibiotic that blocks translocation would therefore prevent the P-site tRNA, with its attached polypeptide chain, from moving to the next stage of the process, effectively inhibiting protein synthesis.