AP BIOLOGY

Detailed explanation-1: -The initiator tRNA molecule carrying the amino acid methionine binds to the AUG start codon of the mRNA transcript at the ribosome’s P site where it will become the first amino acid incorporated into the growing polypeptide chain.

Detailed explanation-2: -The P-site (for peptidyl) is the second binding site for tRNA in the ribosome. The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), the third. During protein translation, the P-site holds the tRNA which is linked to the growing polypeptide chain.

Detailed explanation-3: -3) Translocation: the ribosome moves one codon over on the mRNA toward the 3’ end. This shifts the tRNA in the A site to the P site, and the tRNA in the P site to the E site. The empty tRNA in the E site then exits the ribosome.

Detailed explanation-4: -The P-tRNA ASL moves with the 30S head into a position between the P site of the 30S head and the E site of the 30S body (pe chimeric state; Fig. 1, D and E), while its acceptor end moves fully into the 50S E site (Fig. 1C), forming a pe/E chimeric hybrid state (9–11).

Detailed explanation-5: -The P site, called the peptidyl site, binds to the tRNA holding the growing polypeptide chain of amino acids. The A site (acceptor site), binds to the aminoacyl tRNA, which holds the new amino acid to be added to the polypeptide chain.