Ribosomes are the sites of protein synthesis. All cells share these common features. Ribosomes are small organelles made of protein and RNA that direct protein synthesis in the cytoplasm. They do not have a membrane.
Some ribosomes are free in the cell. Others are attached to the rough endoplasmic reticulum. In eukaryotes, functional ribosomes are found free in the cytoplasm, in mitochondria it is bound to the endoplasmic reticulum.