Which component is found in both prokaryotic and eukaryotic cells?

Ribosomes are found in both prokaryotic and eukaryotic cells because they are essential for protein synthesis, a fundamental process for all living organisms. Ribosomes consist of ribosomal RNA (rRNA) and proteins, and they serve to translate messenger RNA (mRNA) into polypeptides. In prokaryotes, ribosomes float freely in the cytoplasm, while in eukaryotes, they can be found both in the cytoplasm and on the rough endoplasmic reticulum. This universal presence highlights their critical role in the basic biological function of all cells.

The other options present structures or components that are not universally found in both types of cells. A capsule is a protective layer found primarily in some prokaryotic species, particularly bacteria, but is not present in eukaryotic cells. The nucleus is a membrane-bound organelle characteristic of eukaryotic cells, therefore it is absent in prokaryotes, which lack this compartmentalization. Mitochondria are also organelles unique to eukaryotic cells, involved in energy production, and are completely absent in prokaryotic cells. Hence, ribosomes are the only component listed that is common to both prok