Eukaryotes vs. Prokaryotes

Cells are divided into two broad categories: prokaryotic cells and eukaryotic cells. Prokaryotic cells include the single-cell organism bacteria and archaea. Animal cells, plant cells, protists, and fungi are eukaryotes. Viruses are not included in these categories as viruses are not independently living organisms but are dependent on living cells as hosts in order to replicate.

All living cells share five components: a plasma membrane, cytoplasm, DNA, ribosomes and a cytoskeleton. However, eukaryotes and prokaryotes differ in many different ways.

Eukaryotic cells contain more specialized organelles, such as the endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes compared to prokaryotes.

The eukaryotic ribosomes are larger. They consist of a 60S large subunit and 40S small subunit which comes together to form an 80S complete ribosome whereas the prokaryotic cells have 70S ribosomes. The DNA of eukaryotes is contained within a nucleus whereas prokaryotic DNA is found freely in the cytoplasm in a region called the nucleoid.

Prokaryotes also contain plasmids, which are small circular DNA fragments known that have the ability to replicate independently of nuclear DNA. It was thought to be a feature of prokaryotic or bacterial cells throughout the majority of the century but according to later scientific findings, they are also present in some eukaryotic cells. Plasmids have been discovered naturally in fungi and certain higher plants, but it is still unclear if they exist in animal cells.