Where are proteins produced within cells?

Answer 1

Proteins are produced in the cytoplasm, in the rough endoplasmic reticulum, in mitochondria, and in chloroplasts.

Proteins consist of one or more polypeptide chains. Polypeptides are synthesized by ribosomes as they travel along strands of messenger RNA. This synthesis begins at free (unattached) ribosomes in the cytoplasm, but as it proceeds some ribosomes are moved to the rough endoplasmic reticulum and embedded in its membrane. Whether a ribosome is moved depends on the sequence of amino acids in the first part of the polypeptide chain to be translated. The polypeptides that are produced in the endoplasmic reticulum complete their coiling and folding (secondary and tertiary structure) within the lumen of the endoplasmic reticulum, where some of them will also combine with other chains to form more complex proteins (quaternary structure). Proteins synthesized in the rough endoplasmic reticulum are destined for certain sites, e.g. the endoplasmic reticulum itself, lysosomes, the plasma membrane, or for secretion from the cell. Those that are leaving the endoplasmic reticulum pass through the Golgi body, where they may be further processed, e.g. with the addition of oligosaccharide components. Proteins whose synthesis is completed in the cytoplasm at free ribosomes go to other destinations, such as the nucleus, mitochondria, and chloroplasts. The mitochondria and chloroplasts, which are thought to be descendants of ancient free-living prokaryotic cells, have some genes of their own and synthesize some proteins using their own transcription and translation machinery, including their own (prokaryote-like) ribosomes.

Answer 2

proteins are produced in ribosomes