Final answer:
The statement is true, as the Unfolded Protein Response (UPR) is activated by the accumulation of unfolded proteins in the ER lumen to restore normal cell function.
Step-by-step explanation:
True, the Unfolded Protein Response (UPR) is indeed triggered by the accumulation of unfolded proteins in the ER lumen. The ER has a critical role in correctly folding and modifying proteins. When proteins do not fold properly, they accumulate, and this accumulation can cause stress in the ER, which then activates the UPR. This pathway helps in restoring normal function by halting protein translation, degrading misfolded proteins, and activating the signaling pathways that increase the production of molecular chaperones involved in protein folding.