Scientists 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/are possible explanations for the greater length of these polypeptides?
A) The ribosomes that function as free ribosomes function differently than the ribosomes that are attached to the endoplasmic reticulum.
B) The 20- amino- acid sequence helps the endoplasmic reticulum package these proteins for shipping to the Golgi.
C) The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing.
D) The protein has a different function in the cytosol than in the endoplasmic reticulum.

Question

Quizplus · Accepted Answer

The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing. This signal sequence is necessary for the polypeptide to be recognized and transported to the endoplasmic reticulum, and it is removed once the polypeptide reaches its destination.

Scientists Found That Polypeptides That Are Normally Synthesized in the Endoplasmic