Question

What occurs in the endoplasmic reticulum (ER) when misfolded proteins accumulate?

A) Activation of protein synthesis
B) Initiation of apoptosis
C) Unfolding of misfolded proteins
D) Initiation of the unfolded protein response (UPR)

Answer 1

Accumulation of misfolded proteins in the ER triggers the unfolded protein response, a mechanism to restore normal cell function; if unresolved, it may lead to apoptosis.

Step-by-step explanation:

When misfolded proteins accumulate in the endoplasmic reticulum (ER), the cell initiates the unfolded protein response (UPR). The UPR is a cellular stress response related to the ER stress and serves to restore normal function of the cell by halting protein translation, degrading misfolded proteins, and activating the signaling pathways that lead to increased production of molecular chaperones involved in protein folding.

If the misfolded proteins continue to accumulate and the stress is not resolved, the UPR can also trigger apoptotic pathways, potentially leading to programmed cell death. This process ensures that cells with dysfunctional proteins do not continue to survive and potentially cause harm to the organism.