There are more than four organelles that are common to most eukaryotic cells, with organelles such as the nucleus, mitochondria, Golgi apparatus and ribosomes. Other organelles common to eukaryotic cells include the lysosomes, endoplasmic reticulum, vacuoles, chloroplasts and cell walls.
A eukryotic cell defines any cell that contains a nucleus in addition to other organelles. Many eukaryotic cells are plant cells, so they contain chloroplasts and cell walls so that the process of photosynthesis can occur. Prokaryotic cells, in contrast, have no nucleus and are single-celled organisms that also lack other organelles. Bacteria is a common example of a prokaryotic cell.