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Protein Synthesis - Medical Science

Q1:

The direction of amino acid transfer to the growing polypeptide chain is

A from the A (aminoacyl tRNA site) site to the P (peptidyl tRNA site) site on the ribosome

B from the P site to the A site on the ribosome

C from the A site to the E (exit tRNA site) site on the ribosome

D from the P site to the E site on the ribosome

ANS:B - from the P site to the A site on the ribosome

As we know, the ribosome has three active sites: the A site, the P site, and the E site.

The A site is the point of entry for the aminoacyl-tRNA (except for the first aminoacyl-tRNA, fMet-tRNAfMet, which enters at the P site).

The P site is where the peptidyl-tRNA is formed in the ribosome.

And the E site which is the exit site of the now uncharged tRNA after it gives its amino acid to the growing peptide chain.

So please explain the answer.