Which ribosomal site is the Exit site?

Which ribosomal site is the Exit site?

• A. Exit site
• B. Peptidyl site
• C. Aminoacyl site
• D. Terminal site

Answer: (A)

The main idea is how tRNA moves through the ribosome during translation. There are three binding sites: the aminoacyl site (where a new tRNA carrying an amino acid enters), the peptidyl site (where the growing polypeptide chain is held), and the exit site (where tRNA leaves the ribosome after it has donated its amino acid). The exit site is named for this departing role: after the peptide bond forms, translocation shifts the tRNAs so the peptidyl-tRNA moves into the peptidyl site and the now-empty tRNA moves into the exit site and exits the ribosome. The term “Terminal site” isn’t used in standard ribosome terminology, and the other two sites correspond to entry of aminoacyl-tRNA and holding the growing chain. So the exit site is the place where tRNA leaves the ribosome.

The main idea is how tRNA moves through the ribosome during translation. There are three binding sites: the aminoacyl site (where a new tRNA carrying an amino acid enters), the peptidyl site (where the growing polypeptide chain is held), and the exit site (where tRNA leaves the ribosome after it has donated its amino acid). The exit site is named for this departing role: after the peptide bond forms, translocation shifts the tRNAs so the peptidyl-tRNA moves into the peptidyl site and the now-empty tRNA moves into the exit site and exits the ribosome. The term “Terminal site” isn’t used in standard ribosome terminology, and the other two sites correspond to entry of aminoacyl-tRNA and holding the growing chain. So the exit site is the place where tRNA leaves the ribosome.