Question

What happens if a vesicle containing the retention signal KDEL moves out of the ER?

a) Increased protein synthesis
b) ER stress response
c) Apoptosis
d) Protein degradation

Answer 1

The KDEL retention signal is integral for proteins destined to remain in the endoplasmic reticulum. If a vesicle with KDEL-tagged proteins exits the ER, it is retrieved and returned to the ER, thus option c is correct.

Step-by-step explanation:

KDEL signal is a retention signal for proteins that are supposed to remain in the endoplasmic reticulum (ER). When a vesicle containing a protein with the KDEL signal mistakenly moves out of the ER, there is a retrieval mechanism that recognizes this signal and returns the protein to the ER. Thus, the correct answer to the question, 'What happens if a vesicle containing the retention signal KDEL moves out of the ER?' is c. The vesicle travels from the endoplasmic reticulum to the plasma membrane, and returns to the Golgi apparatus to get modified. This ensures that enzymes and other proteins with specific functions in the ER do not end up in other parts of the cell, where they could disrupt normal cell functions or be degraded.