When Translating Secretory or Membrane Proteins, Ribosomes Are Directed to the ER

Multiple Choice

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by

A) a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes.
B) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.
C) moving through a specialized channel of the nucleus.
D) a chemical signal given off by the ER.
E) a signal sequence of RNA that precedes the start codon of the message.