Which of the following properties is associated with a protein that will be secreted from a eukaryotic cell?
A) It must be translated by a ribosome that remains free within the cytosol.
B) Its signal sequence must target it to the ER, after which it goes to the Golgi.
C) Its signal sequence must be cleaved off before the polypeptide can enter the ER.
D) Its signal sequence must target it to the plasma membrane, where it causes exocytosis.

Question

Quizplus · Accepted Answer

A signal sequence is required for targeting the protein to the endoplasmic reticulum (ER), where it will undergo further processing and modification before being transported to the Golgi and eventually secreted from the cell. Option A is incorrect because if a protein is secreted, it must be translated by a ribosome bound to the ER membrane, not a free ribosome in the cytosol. Option C is partially correct, but the signal sequence is not cleaved off before entering the ER, it is recognized by signal recognition proteins and integrated into the ER membrane. Option D is incorrect because not all secreted proteins are targeted to the plasma membrane.

Which of the Following Properties Is Associated with a Protein