Protein secretion

1. From the cytosol, proteins cross (translocate) the ER membrane and exit the ER in vesicles. 2. These vesicles then fuse with the Golgi, and the proteins are transported through the Golgi into secretory vesicles. 3. After fusion of the last vesicles with the plasma membrane, the protein content (cargo) is secreted to the outside of the cell.