Which of the following is NOT a function of the rough endoplasmic reticulum?

The rough endoplasmic reticulum (RER) is primarily associated with the synthesis and processing of proteins, making it an essential component of the cell's protein production machinery. This organelle is studded with ribosomes, which are critical for translating mRNA into polypeptide chains. Once synthesized, proteins often undergo modifications within the RER, such as folding and glycosylation, ensuring they are properly processed before being transported to their final destinations.

While the RER plays a crucial role in protein synthesis and processing, it does not have a function in deciding cell fate. Cell fate decisions are generally determined by complex interactions involving various signaling pathways and factors that influence gene expression, processes that occur within the nucleus and other parts of the cell rather than specifically within the RER.

Therefore, the correct answer identifies a role that is not associated with the rough endoplasmic reticulum, reinforcing the understanding of its specific functions in the cell regarding protein handling.