Prokaryotes
- The prokaryotes are a group of organisms that lack a cell nucleus or any other membrane-bound organelles. They were originally thought to live on in inhospitable conditions but have since been found in all types of habitats.
- The word PROKARYOTES comes from Greek.
- Prokaryotes live in nearly all environments on earth where there is liquid water.
- They are cells in bacteria and archaea and cells are usually independent.
- The oldest known prokaryotes were laid down approximately 3.5 billion years ago, only about 1 billion years after the formation of the Earth's crust.
- Prokaryotes have diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading too many highly distinct prokaryotic types.
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| Cell structure of a bactarium, one of the two domains of prokaryotic life. |
Eukaryotes
- A eukaryote is an organism whose cells contain complex structures enclosed within membrane.
- All species of large complex organisms are eukaryotes (including animals, plants, fungi and protists).
- The word EUKARYOTES also comes from Greek.
- The eukaryotic cells are often found in multicellular organisms.
- The origin of the eukaryotic cell was a milestone in the evolution of life, since they include all complex cells and almost all multi-cellular organisms.
- The presence of steranes indicates that eukaryotes were present 2.7 billion years ago.
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| Structure of a typical plant cell (eukaryote) |
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Structure of a typical animal cell (eukaryote) |
In the world of cells, there are two major groups: the prokaryotes and the eukaryotes. They are very similar in that they contain many of the same parts. However, there are a few major differences between them.
Prokaryote | Eukaryotic Eukaryote | |
Size of cell | Very minute in size, between 1-10 micrometers | Fairly large in size, animal cells are between 10-30 micrometers; most plant cells are between 10-100 micrometers |
Nucleus | Do not have a nucleus | True nucleus |
Membrane-enclosed organelles | Absent | Present |
Flagella | Consist of two protein building blocks | Complex: consists of multiple microtubules |
Cilia | Complex | Simple |
Cell Wall | Usually present | Present in animals, not present in plants |
Plasma membrane | No carbohydrates and lacks sterols | Sterols and carbohydrates present that serve as receptors |
Cytoplasm | No cytoskeleton | Cytoskeleton with cytoplasmic |
Ribosomes | Smaller size | Large size except in organelles when smaller |
Chromosome | Single chromosome present | More than one chromosome present |
Cell division | By fission or budding | By mitosis or meiosis |
Sexual reproduction | Transfer of DNA fragments only and is always asexual | Involves meiosis and is asexual or sexual |
Metabolic | Huge of metabolic pathways | Common metabolic pathways |
Endoplasmic reticulum | Absent | Present |
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| Differences between Prokaryote and Eukaryote |
source: http://www.daviddarling.info/encyclopedia/E/eukarycell.html
http://en.wikipedia.org/wiki/Cell_%28biology%29
http://en.wikipedia.org/wiki/Eukaryote
http://en.wikipedia.org/wiki/Prokaryote
http://www.allfreeessays.com/essays/Evolutionary-Relationship-Between-Prokaryotic-Eukaryotic-Cells/2603.html
http://intranet.canacad.ac.jp:3445/bioibsl1/4424
http://en.wikipedia.org/wiki/Cell_%28biology%29
http://en.wikipedia.org/wiki/Eukaryote
http://en.wikipedia.org/wiki/Prokaryote
http://www.allfreeessays.com/essays/Evolutionary-Relationship-Between-Prokaryotic-Eukaryotic-Cells/2603.html
http://intranet.canacad.ac.jp:3445/bioibsl1/4424
http://www.youtube.com/watch?v=nP9lZG94DO0
