Abstract
The free and membrane-bound ribosomes of hepatic cells were isolated and used to program protein synthesis in cell-free extracts. Immuno-electrophoretic and radioautographic analysis of the products showed that the membrane-bound ribosomes synthesized serum proteins, whereas ribosomes free of endoplasmic reticulum synthesized specific nonserum liver proteins. After synthesis, the serum proteins remained associated with membrane vesicles, whereas the other liver proteins were found free of cytoplasmic organelles.