07. prokaryotes short - 9/25/2008 1 The three main branches...

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9/25/2008 1 1 The three main branches of life 2 • Genes located on a single circular chromosome and sometimes on smaller plasmids • Chromosomes not separated into a membrane- bound nucleus The two domains of prokaryotic organisms are the Bacteria and the Archaea • No membrane-bound organelles or endoplasmic reticulum • Ribosomes embedded in the cytoplasm • No cytoskeleton • No mitosis, meiosis, or gametes • Flagella, if present, a simple protein filament that rotates at its base 3 Domain Bacteria The bacterial cell wall is made up primarily of peptidoglycan, and serves in osmoregulation and defense The interior contains DNA in a folded circular loop and cytoplasm with ribosomes Flagella serve for motility Pili allow bacteria to stick to a substrate or to each other 4 The walls around bacterial cells are complex Gram-positive bacteria have a thick wall of peptidoglycan, while gram-negative bacteria have a thinner wall with an additional outer phospholipid membrane; a periplasmic space forms between the inner and outer membranes Some bacteria have a polysaccharide capsule around the outside 5 Internal membrane systems are found in aerobic (L) and photosynthetic (R) bacteria. Why?
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This note was uploaded on 02/10/2010 for the course BSC 2010 taught by Professor Essig during the Spring '10 term at University of Southern Maine.

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07. prokaryotes short - 9/25/2008 1 The three main branches...

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