Grouping organisms into prokaryotes and eukaryotes allows us to distinguish between 2 patterns of cellular organization. Bacteria and archae make up the prokaryotes (Pro-karytoes = before nucleus). While cells with a membrane bound nucleus and organelles make up the eukaryotes. Eukaryotes include plants, animals, and blue-green algae.
More Differences between Prokaryotes and Eukaryotes
Although the presence or absence of a membrane bound nucleus is the major criteria separating prokaryotes from eukaryotes, other characteristics such as size and the presence of organelles differentiate the 2 major patterns of cellular organization.
Prokaryotes (bacteria) are much smaller than eukaryotic cells. Since bacteria are much smaller than eukaryotes it is common to see bacteria living in or on eukaryotic organisms.
Organelles are compartmentalized workhorses of eukaryotic cells that allow them to produce energy, make proteins, and synthesize many other cellular components. Prokaryotes may have ribosomes (make proteins), but they do not have many organelles that carry out more complex tasks. For example eukaryotes use mitochondria to make ATP(cellular energy) while bacteria must rely on their cell membrane to produce ATP.
It is generally observed that prokaryotes are unicellular while eukaryotes are multicellular organisms. However there are exceptions to this general observation. For example the “brain eating” amoebae, N. fowleri, is an exception to the rule because it is a unicellular eukaryotes. So despite many observed difference like size and cellularity, the presence or absence of membrane bound nucleus and organelles are the true separator.
A Simple Summary of what you read
- This 2 tier grouping of all organisms has been accepted as early as the 1940’s to divide organisms into groups based on cellular organization.
- Prokaryotes do not have a membrane bound nucleus or membrane bound organelles.
- Eukaryotes have a membrane bound nucleus and organelles which compartmentalize many functions.
- Eukaryotes and prokaryotes generally differ in cell size and cellularity. Eukaryotes are usually larger and multicellular.
- Prokaryotes are normally smaller than eukaryotes, and unicellular.