Question

Scientists have found that polypeptides that are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. what is a possible explanation for the greater length of these polypeptides?

Answer 1

The best possible explanation is that the 20 amino acids serve as a signal (peptide) sequence that directs the forming polypeptides to the endoplasmic reticulum, where they are cleaved off during processing.