Two categories of cells are prokaryotes and eukaryotes. The first types of cells to evolve, were prokaryotic cells- organisms that lack a nuclear membrane, the membrane that surrounds the nucleus of a cell.
Prokaryotic cells have three architectural regions: appendages called flagella and pili-proteins attacked to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma member; and a cytoplasmic region that contains the cell genome(DNA) and ribosomes.
Eukaryotes include fungi, animals, and plants as well as some unicellular organisms. Eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Eukaryotic organisms also have other specialized structures, called organelles, which are small structures within cells that perform dedicated formulas. Without eukaryotic, the world would lack mammals, fish, birds, invertebrates, mushrooms, plants, and complex single-celled organisms.
(http://www.ncbi.nlm.nih.gov/About/primer/genetics_cells.html)
Posted by planet/lisa4
at 7:10 PM EDT
Updated: Wednesday, 9 May 2007 7:10 PM EDT
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Updated: Wednesday, 9 May 2007 7:10 PM EDT
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