Final answer:
The polypeptide is driven through the translocon in the ER by translocation, facilitated by elongation factors such as EF-G and translocase.
Step-by-step explanation:
The polypeptide is driven through the translocon in the endoplasmic reticulum (ER) by a process called translocation. During elongation, the growing polypeptide moves through a translocation channel with the help of elongation factors, such as elongation factor-G (EF-G) or translocase. GTP, a molecule similar to ATP, provides the energy for each step along the ribosome, including binding of new aminoacyl-tRNA to the A site and translocation to the P site after peptide bond formation.