Which cellular organelle is responsible for synthesizing proteins that are exported from the cell?

The rough endoplasmic reticulum (Rough ER) is studded with ribosomes on its cytoplasmic surface, giving it a "rough" appearance. These ribosomes are the sites of protein synthesis, where messenger RNA (mRNA) is translated into polypeptide chains. The Rough ER plays a crucial role in synthesizing proteins that are either secreted from the cell, incorporated into the cell's plasma membrane, or sent to organelles. After synthesis, these proteins enter the lumen of the Rough ER for further folding and modification before being transported to the Golgi apparatus for processing and eventual export from the cell. This organelle is integral to the secretory pathway, making it essential for the production of proteins that are destined to leave the cell.