So basically, this process by which our growing polypeptide chain is transported from the cytoplasm onto the membrane of the endoplasmic reticulum, is known as translocation. And the mechanism by which it actually takes place involves the signal sequence and the signal recognition particles. So those growing polypeptides, those proteins that actually are destined to be secreted by the cell or remain in the plasma membrane, contain this signal sequence. And it's the signal sequence that basically allows the signal recognition particles to recognize it, to bind to it, and to bring the entire growing polypeptide chain, as well as the free ribosome, and bring that ribosome onto the membrane of the endoplasmic reticulum. And once that binding takes place, the free ribosome becomes a membrane bound ribosome. So these membrane bound ribosomes are responsible for synthesizing proteins that are ultimately and that ultimately end up being secreted by the cell or being embedded inside the plasma membrane of the cell.