Download Prokaryotic and Eukaryotic Cells: The Difference between

Prokaryotic and Eukaryotic Cells: The Difference between
Prokaryotes and Eukaryotes
There are only two basic types of cells, primitive prokaryotes and the more complex eukaryotes. Here are the
main features that distinguish these cell types.
What Is a Cell?
Living things are constructed of cells and can be unicellular (one cell) or multicellular (many cells). Cells size
is limited because cells must be able to exchange materials with their surroundings. In other words, surface area
relative to the volume decreases as size of cell increases, and this limits the size of cells. Only a few hundred
years ago it was believed that living things could spontaneously generate from non-living matter -- abiogenesis.
We now know better. Cell theory lays out the basic rules that apply to the smallest unit of life. This cell doctrine
states that:



All organisms are composed of one or more cells.
Cells are the basic unit of structure and function in organisms.
All cells come only from other cells.
Two Basic Types of Cells
All cells fall into one of the two major classifications: prokaryotes or eukaryotes.
Prokaryotes are evolutionarily ancient. They were here first and for billions of years were the only form of life.
And even with the evolution of more complex eukaryotic cells, prokaryotes are supremely successful. All
bacteria and bacteria-like Archaea are prokaryotic organisms.
Eukaryotic cells are more complex, evolving from a prokaryote-like predecessor. Most of the living things that
we are typically familiar with are composed of eukaryotic cells; animals, plants, fungi and protists. Eukaryotic
organisms can either be single-celled or multi-celled.
Features of Prokaryotes (Pro = “before”,
karyon = “nucleus”)
Prokaryotes, the first living organisms to evolve, are
primarily distinguished by the fact that they lack a
membrane-bound nucleus. In fact, the only
membrane in prokaryotic cells is the plasma
membrane--the outer boundary of the cell itself.
Their genetic material is naked within the
cytoplasm, ribosomes their only type of organelle.
Diagram of Prokaryotic Cell
Prokaryotes are most always single-celled, except
when they exist in colonies. These ancestral cells,
now represented by members of the domains
Archaea and Eubacteria, reproduce by means of
binary fission, duplicating their genetic material and
then essentially splitting to form two daughter cells
identical to the parent.
Features of Eukaryotes (Eu = “true”,
karyon = “nucleus”)
The most noticeable feature that differentiates these
more complex cells from prokaryotes is the
presence of a nucleus, a double membrane-bound
control center separating the genetic material, DNA
(deoxyribonucleic acid), from the rest of the cell.
Diagram of Eukaryotic Plant Cell
In addition to the plasma membrane, eukaryotic
cells contain internal membrane-bound structures
called organelles. Organelles, such as mitochondria
and chloroplasts, are both believed to have evolved
from prokaryotes that began living symbiotically
within eukaryotic cells. These vital organelles are
involved in metabolism and energy conversion
within the cell. Other cellular organelles within
eukaryotic cell structure carry out the many
additional functions required for the cell to survive,
thrive, grow and reproduce.
Eukaryotic cells can reproduce in one of several
ways, including meiosis (sexual reproduction) and
mitosis (cell division producing identical daughter
cells).
Diagram of Eukaryotic Animal Cell
Sources
Bauman, R. (2005) Microbiology.
Park Talaro, K. (2008) Foundations in Microbiology.
Written by Tami Port
Accessed 10-1-2007