AAT Bioquest

Where are ribosomes located?

Posted October 13, 2022


Ribosomes are located in different parts of cells, and their location is dependent on the cell type. Both eukaryotic and prokaryotic cells have ribosomes freely floating in their cytoplasms, known as free ribosomes. In eukaryotes, ribosomes begin in the nucleolus, where ribosomal RNA is synthesized and bound there. They are then exported to create ribosomes; in prokaryotes this process is completed in the cytoplasm. Ribosomes are also located in the ER, which they attach to and become fixed ribosomes. Proteins are made in the rough ER and transported through the smooth ER to become part of the cell membrane or other products for cell consumption. Some eukaryotes contain ribosomes in their mitochondria, where they also perform protein synthesis, and are known as mitoribosomes. 70S ribosomes have chloroplast ribosomes, also for protein synthesis.   

Additional resources

The Road to Ribosomes

Endoplasmic Reticulum (ER)

DNA and RNA Quantitation