Question

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

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

Answer 1

Ribosomes are directed to the ER membrane by a signal-recognition particle (SRP) that brings ribosomes to a receptor protein in the ER membrane.

Step-by-step explanation:

In the process of protein synthesis, ribosomes are directed to the ER membrane by a signal-recognition particle (SRP) that brings ribosomes to a receptor protein in the ER membrane. The SRP binds to the hydrophobic signal peptide of the protein being synthesized, and the SRP-ribosome complex finds the RER membrane by interacting with an SRP receptor. This allows for the correct targeting and insertion of secretory or membrane proteins into the ER membrane.