AAT Bioquest

What are the differences between free and attached ribosomes?

Posted January 10, 2023


Free and attached ribosomes are both involved in synthesizing proteins through the translation of messenger RNA (mRNA). There are a few key differences between the two.  

Free Ribosomes

Free ribosomes are small organelles that float freely in the aqueous cytosol. They are not attached to any cellular structure and can move unhindered all around the cell. Free ribosomes synthesize proteins that stay in the cytosol to be used within the cell itself. Proteins produced by free ribosomes include enzymes that are involved in the metabolism of macromolecules, contractile proteins in muscle cells and hemoglobin in red blood cells. These proteins are also used by the mitochondria, which is the energy center of the cell and in the cytoskeleton, an important supportive structure. Several cellular components would be unable to function without proteins produced by the free ribosomes. 


Attached Ribosomes

Attached ribosomes are small organelles that are anchored to the cytosolic side of the rough endoplasmic reticulum at docking stations known as translocons. Once these ribosomes get attached to the rough ER, they cannot move to other areas of the cell and remain in a fixed position on the surface of the rough ER. Attached ribosomes synthesize proteins that are transported out of the cell via secretory vesicles. Proteins synthesized by attached ribosomes include cell surface receptors, digestive enzymes, cell signaling molecules, and polypeptide hormones.

Additional resources

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