Final answer:
In the context of protein synthesis, if an antibiotic blocks the scanning process during initiation, the A site on the ribosome would be occupied by nothing, as tRNA entry and peptide bond formation have not yet initiated.
Step-by-step explanation:
During the initiation phase of protein synthesis, if an antibiotic inhibitor blocks the scanning reaction, at the inhibited ribosome, the A site will be occupied by nothing. This is because, during initiation, the A site has not yet accommodated an aminoacyl tRNA, which only enters during the elongation phase. Antibiotics such as tetracycline, which block the A site, would directly affect tRNA binding to the ribosome and therefore inhibit the growth of the protein chain by preventing new aminoacyl tRNAs from entering the A site and adding their amino acids to the polypeptide chain. In contrast, antibiotics like chloramphenicol would affect the growth of the protein chain by blocking peptidyl transferase activity and thereby preventing peptide bond formation between amino acids at the P and A sites of the ribosome.