Ribosomes are found in both prokaryotic and eukaryotic cells, located in several places depending on the cell type. In both types of cells, ribosomes can be found freely floating in the cytoplasm, known as free ribosomes. In eukaryotic cells, ribosomes also attach to the rough endoplasmic reticulum (ER), making the ER appear "rough," and these are called membrane-bound ribosomes. Furthermore, in eukaryotic cells, ribosomes begin forming in the nucleolus of the nucleus where ribosomal RNA is synthesized. Ribosomes are also present in mitochondria of eukaryotic cells and chloroplasts in plant cells, where they aid in protein synthesis for those organelles. To summarize:
- Free ribosomes float in the cytoplasm.
- Membrane-bound ribosomes are attached to the rough ER.
- Ribosomes form initially in the nucleolus (eukaryotes).
- Mitochondria and chloroplasts also contain ribosomes.
- In prokaryotes, ribosomes are found in the cytoplasm.
This distribution facilitates their main role of protein synthesis in various cellular regions and organelles.
