In eukaryotes, the signal peptide of a nascent precursor protein (pre-protein) directs the ribosome to the rough endoplasmic reticulum ... the pre-protein to the cytoplasmic membrane.

Cells that produce large amounts of protein have cytoplasmic dye- and radiation ... other membranous organelles (such as the endoplasmic reticulum), and finally a microsomal fraction of smaller ...