Learn something new every day More Info... by email
Prokaryotic and eukaryotic cells are the two basic forms cells can take. Prokaryotic cells form single-cell organisms such as bacteria and archaea, while eukaryotic cells are the basis of all other types of life. In terms of the evolution of the Earth, prokaryotic cells came first and were later superseded by their eukaryotic counterparts.
The most noticeable difference between prokaryotic and eukaryotic cells is the latter’s ability to form a complex organism. Prokaryotes are all single-cell organisms while eukaryotes include plants, fungi, and animals. The ability to combine and cooperate has allowed eukaryotes to develop far beyond prokaryotes.
Both cell types contain elements similar to one another. Both types are deoxyribonucleic acid (DNA) based organisms containing a cell membrane, flagellum, cytoplasm, and ribosomes. They share the same kind of DNA and the same kind of genetic code. One difference is that a prokaryote’s DNA is circular while a eukaryote’s is linear. Eukaryotic DNA binds with histone proteins to form chromosomes, while prokaryotic DNA does not.
The most notable physiological difference between prokaryotic and eukaryotic cells is the former’s lack of a true nucleus. A nucleus contains and processes the majority of the eukaryotic cell’s DNA, and its function is to control cellular activity. The nucleus is contained within a membrane to keep it separate from the rest of the cell. The prokaryote has a nucleoid center where DNA is gathered, but there is no separating membrane.
Internal membranes are a recurring difference between the two cell types. A eukaryotic cell is filled with distinct miniature organs called organelles. These membrane-bound elements perform specific functions within the cell and are distinct from the cell’s cytoplasm. Prokaryotes tend to have no organelles separated from the cytoplasm. Cytoplasm is a viscous liquid contained within a cell.
While both prokaryotic and eukaryotic cells have ribosomes, the ribosomes in eukaryotic cells are larger and more developed. Ribosomes use amino acids and ribonucleic acid (RNA) to create proteins within the cell. A prokaryotic ribosome is made up of three kinds of ribosomal RNA (rRNA) and about 50 types of protein. The eukaryotic ribosome, however, consists of five types of rRNA and around 80 types of protein.
Eukaryotic cells contain a distinct organelle called a mitochondrion, and plant cells also have organelles called plastids. Prokaryotic cells have neither. Mitochondria and plastids seem to have a common origin. Both appear to have been distinct prokaryotes absorbed within eukaryotes in a permanent symbiotic relationship.
Some generalized differences are complicated by exclusions. As a general rule, prokaryotic and eukaryotic cells differ over cell walls. While all prokaryotes have them and most eukaryotes do not, there are exceptions. Some prokaryotes have developed primitive organelles, but generally, they are absent.