5 Facts On Protein Synthesis In Endoplasmic Reticulum

Protein synthesis is the process through which rRNA, tRNA, mRNA, and other enzymes linearly arrange amino acids into proteins. Let us know more about protein synthesis in ER.

The endoplasmic reticulum plays a key role in protein synthesis. On the surface of endoplasmic reticulum an intracellular structure made up of RNA and protein, called ribosomes is present. This ribosome is the main site of protein synthesis. After the synthesis, amino acid is transported to the ER .

Proteins are introduced into ER, then transported through Golgi body on their way to their eventual destinations, which may be cell wall, vacuole, or one of the other chambers of endomembrane system.

Let us discuss if endoplasmic reticulum synthesis proteins, how protein synthesis happen in ER, where protein synthesis happen in ER and many other related questions in this article.

Does endoplasmic reticulum synthesis proteins?

Numerous cellular products are produced, packaged, and secreted by endoplasmic reticulum. Let us see if endoplasmic reticulum synthesis proteins.

Rough endoplasmic reticulum does synthesis protein. All proteins start their translation in the cytoplasm, however some are transported into the ER to be folded and sorted for various destinations.

These proteins are initially folded in ER before being transported to the Golgi apparatus, where they can then be sent to other organelles.

Where does protein synthesis happen in endoplasmic reticulum?

The eukaryotic cell’s endoplasmic reticulum (ER) serves a variety of crucial roles in the cell. Let us find out where protein synthesis happens in endoplasmic reticulum.

Protein synthesis happen in the cisternae form of rough endoplasmic reticulum. RER’s ribosomes, which are responsible for the rough appearance of RER, specialise in the synthesis of proteins with signal sequences that send them directly to the ER for processing.

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Protein synthesis from Wikimedia

The cell membrane, the cell surface, or even the ER itself are among the places where proteins created by the RER ultimately end up.

When does protein synthesis happen in endoplasmic reticulum?

The primary organelle for protein synthesis is ribosome which is found on the surface of endoplasmic reticulum (ER). Let us see when protein synthesis happens in ER.

The process of protein synthesis in endoplasmic reticulum is given below:

  • Amino acids i.e., the unit of protein is first arranged by ribosomes in the form of polypeptide on the surface of RER
  • Next, these polypeptides move through RER where they get further modifications.
  • Then, from the Rough ER, transport vesicles containing the proteins are extracted.
  • Transporters interact with the Golgi complex membrane, releasing the proteins inside.
  • The proteins are subsequently processed and stored within the Golgi complex.
  • The Golgi complex produces vesicles that are carriers of the finished proteins.
  • Vesicles move to the cell membrane, affix, and release the protein to the exterior.

This is how the whole process of protein synthesis happen inside endoplasmic reticulum and then the synthesised protein are transported to the outside.

Role of endoplasmic reticulum in protein synthesis:

Ribosomes are affixed to the surface of RER, which is used to produce proteins during translation. Let us understand the role of endoplasmic reticulum in protein synthesis.

Listed below are major roles of endoplasmic reticulum in protein synthesis:

  • The protein secretory route enters cell through the endoplasmic reticulum (ER).
  • Protein folding and further modifications also done inside the endoplasmic reticulum.
  • Several endoplasmic reticulum chaperone proteins enable the proper folding of freshly produced proteins.
  • Additionally, the ER performs a quality control role for proteins.
  • Until proteins achieve their proper shape, they are often kept in this compartment.
  • Some kinds of storage proteins aggregate and accumulate in the ER as well.

What proteins are synthesized in the endoplasmic reticulum?

One of the main roles of the ER in biosynthetic processes is the covalent attachment of sugars to proteins. Let us know what proteins are synthesized in the endoplasmic reticulum.

The well-known milk proteins casein and whey proteins are among the proteins produced by the endoplasmic reticulum. Before merging with the plasma membrane and releasing their contents into the milk ducts, these proteins are bundled into secretory vesicles and transported through the Golgi network.

The majority of the soluble and membrane-bound proteins produced in the ER are glycoproteins, including those going to the Golgi apparatus, lysosomes, plasma membrane, or extracellular space.


The process of translation, which builds proteins from RNA sequences, starts protein synthesis in the cytosol. As the protein develops, it will bind to a signal recognition particle that transports the ribosome to the RER membrane if it has a signal sequence at its amino-terminal end. The signal recognition particle separates once it has been bound to the RER, and protein translation goes on.

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