[Campbell Biology P.399] During polypeptide elongation, how is a new amino acid incorporated... | Practice Question

During polypeptide elongation, how is a new amino acid incorporated and where does the growing polypeptide exit the ribosome?

  • A: New amino acids are added to the amino end, and the polypeptide exits through a tunnel in the small subunit.
  • B: New amino acids are added to the carboxyl end, and the polypeptide exits through an exit tunnel in the large subunit.
  • C: New amino acids are added to the amino end, and the polypeptide exits directly from the P site.
  • D: New amino acids are added to the carboxyl end, and the polypeptide remains attached to the ribosome until termination.

Explanation

The text states: 'The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. Discharged tRNAs leave from the E site. The polypeptide grows at its carboxyl end.' And 'As the polypeptide becomes longer, it passes through an exit tunnel in the ribosome's large subunit.'