Ribosomes produce and assemble all the proteins in the cell. All cells, even very simple ones like bacteria, have ribosomes.
Ribosomes are composed of very large proteins and ribosomal RNA. A ribosome does not have a membrane and therefore is not an organelle.
- Membrane-bound ribosomes are attached to the rough endoplasmic reticulum. They produce proteins used in organelles or outside the cell.
- Free ribosomes float freely in the cell. They produce proteins used within the cell.
Ribosomes give rough endoplasmic reticulum its rough appearance.