There are two general classes of cells: prokaryotic and eukaryotic.
The evolution of prokaryotic cells preceded that of eukaryotic cells by 2
The major similarities between the two types
of cells (prokaryote and eukaryote) are:
- Streptococcus pyogenes, the bacterium
that causes strep throat, is an example of prokaryotes.
the organism that makes bread rise and beer ferment, is an example of
- Humans, of course, are an example of
The major and extremely significant difference
between prokaryotes and eukaryotes is that eukaryotes have a nucleus and membrane-bound
organelles , while prokaryotes do not. The DNA of prokaryotes floats freely
around the cell; the DNA of eukaryotes is held within its nucleus. The
organelles of eukaryotes allow them to exhibit much higher levels of
intracellular division of labor than is possible in prokaryotic cells.
Additional obvious differences between prokaryotes and eukaryotes include:
- They both have DNA as their genetic material.
- They are both membrane bound.
- They both have ribosomes .
- They have similar basic metabolism .
- They are both amazingly diverse in
- Eukaryotic cells are, on average, ten
times the size of prokaryotic cells.
- Genomic composition and length
- The DNA of eukaryotes is much more
complex and therefore much more extnsive than the DNA of prokaryotes.
- Prokaryotes have a cell wall composed of
peptidoglycan, a single large polymer of amino
acids and sugar . Many types of eukaryotic cells also have cell walls, but none
made of peptidoglycan.