BIOL208 Lecture 11: Prokaryotes
29 Mar 2018
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Document Summary
Domains archaea and bacteria form distinct branches, but inherited simple prokaryotic cell organization from a common ancestor. Prokaryotic cells differ from eukaryotic cells in several features: Most prokaryotic cells are small (0. 5-5 um) and unicellular, although some prokaryotes form colonies. Their small size supports high rates of metabolism (because of short diffusion distances), but diffusion limits size in prokaryotic cells. Prokaryotic cells have circular genomes not surrounded by a nuclear membrane (they lack a nucleus) Structural and functional adaptations contribute to prokaryotic success. Nearly all prokaryotic cells have a cell wall: The cell wall maintains shape, protects the cell, and prevents it from bursting in hypotonic environments. Bacterial cell walls contain peptidoglycan, which is a network of sugar polymers cross-linked by polypeptides. Archaea contain polysaccharides and proteins but lack peptidoglycan. Eukaryote cell walls are made of cellulose (plants) or chitin (fungi) Gram stain: can be used to classify bacteria by cell wall composition.
