Prokaryotes and fundamentally different from eukaryotes p547-p549 (Chap28, Raven et al.,)

Bacteria vs. Archaea Plasma membrane –All prokaryotes have a plasma membrane –Bacterial lipids are unbranched Use ester bonds –Archaean membranes are formed on glycerol skeleton with ether linkages (not ester) Hydrocarbons may be branched or have rings Tetraether polymer allows extremophiles to withstand high temperatures 2

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Cell wall –All prokaryotes have cell walls –Bacteria have peptidoglycan –Archaea lack peptidoglycan DNA replication –Both have single replication origin –Archaeal DNA replication is more similar to that of eukaryotes Gene Expression –Archaeal transcription and translation are more similar to those of eukaryotes 4

Early Classification Characteristics Relied on staining characteristics and observable phenotypes 1.Photosynthetic or nonphotosynthetic 2.Motile or nonmotile 3.Unicellular, colony-forming, or filamentous 4.Formation of spores or division by transverse binary fission 5.Importance as human pathogens or not 5

Molecular Classification 1.Amino acid sequences of key proteins 2.Percent guanine–cytosine content 3.Nucleic acid hybridization –Closely related species will have more base pairing 4.Gene and RNA sequencing –Especially rRNA 5.Whole-genome sequencing 6

7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Common ancestor Domain Bacteria Domain Archaea Domain Eukarya