Scientists found that many polypeptides that are normally co-translationally inserted into the endoplasmic reticulum are about 10 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. What is a possible explanations for the greater length of these polypeptides? Group of answer choices The 10 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing. The ribosomes that function as free ribosomes function differently than the ribosomes that are attached to the endoplasmic reticulum. The 10-amino-acid sequence helps the endoplasmic reticulum package these proteins for shipping to the Golgi. The protein has a different function in the cytosol than in the endoplasmic reticulum