2/21/11$–$The$Origin$of$Eukaryotes$$• Testosteroni$–$bacteria$that$survives$on$testosterone.$$• Prokaryotes$have$more$metabolic$diversity$than$eukaryotes$–$many$that$can$live$in$boiling$hot$springs,$can$live$in$rocks,$live$off$of$testosterone,$eukaryotes$cannot$do$that.$• Prokaryotes$have$immense$metabolic$diversity$compared$to$eukaryotes.$• Prokaryotes$have$only$a$few$body$plans,$very$low$structural$diversity$• Multicellular$life$is$all$eukaryotes.$• Eukaryotic$cells$are$complex,$not$an$accident.$Their$abilitiy$to$reach$larger$size$is$directly$related$to$their$complexity.$• Limits$of$prokaryotes$–$small$size$and$simple$structure$so$they$are$limited$with$their$genome$size.$Very$poor$at$multitasking,$do$one$task$and$do$it$very$well.$One$task$at$a$time.$To$get$away$from$these$restrictions,$there$had$to$be$a$revolution$in$cell$structure.$• 3$innovations$to$eukaryotic$development$–$1.$Origin$of$the$nucleus$• urkaryotes$–$earliest$eukaryotic$cells,$evolved$before$the$appearance$of$mitochondria$or$chloroplasts$or$any$other$plastids.$They$contain$a$nucleus$but$are$anaerobic$and$heterotrophic.$Urkaryote$=$anaerobic,$heterotrophic$cell$with$a$nucleus.$$• Complex$nuclear$membrane$around$the$nucleus$–$why$is$it$there?$Seperates$chromosomes$from$the$cytoplasm,$protects$the$dna$from$water,$dna$has$many$polar$groups$so$if$its$in$water$it$would$come$apart.$Dna$must$b$protected$from$water$–$point$of$nuclear$membrane.$It$allows$bigger$chromosomes$to$evolve.$• Planctomycetes$–$have$a$nucleusOlike$structure.$Not$a$true$eukaryotic$nucleus$but$every$similar.$Have$a$more$complex$genome$with$a$double$membrane$around$nucleoid.$Membrane$protects$from$the$hydration$shell$of$water.$In$prokaryotic$cells,$transcription$and$translation$occur$simultaneously.$This$is$different$in$eukaryotes.$In$this$prokaryote,$it$made$transcription$and$translation$occur$separately,$more$like$eukaryotes.$Decoupled$transcription$and$translation.$No$other$group$of$prokaryotes$do$that.$This$is$how$the$nucleus$probably$started$evolving.$Larger$genome,$nuclear$membrane$to$protect$from$water$and$decouple$transcription$and$translation.$• Origin$of$eukaryotes$–$know$engulfment$and$fusion$in$the$graph.$Engulfment$and$fusion$are$related$to$the$evolution$$of$the$nucleus.$Symbiosis$theory$is$related$to$the$evolution$of$the$mitochondria$and$plastids.$$• Nuclear$evolution$–$most$of$the$processes$that$occur$in$the$cytoplasm$–$metabolism,$stress$response,$detoxification,$and$ionic$homeostasis$are$related$to$bacterial$ancestors.$All$of$the$things$that$happen$in$the$nucleus$are$genes$that$are$relatd$to$an$archaen$ancestor.$Only$way$that$occurs$is$if$there$is$some$sort$of$fusion$or$engulfment.$$• Mitochondrial$evoluton$–$endosymbiosis$an$anaerobic$urkaryote$engulfs$an$aerobic$prokaryote.$Proof$on$slides.$Molecular$evidenceO$sequence$of$genes$is$very$similar$between$the$2.$Have$a$recent$common$ancestor.$$• ETC$–$build$up$concentration$gradient$of$protons,$3$complexes,$2$shuttles$• Graph$on$slide$comparing$etc$of$photosynthesis$and$cell$resp.$• All$etcs$are$the$same.$All$etcs$are$a$modification$of$the$same$pattern$that$occurred$in$the$evolution$of$life$on$this$planet.$Suttle$modifications$of$the$same$thing.$$• Mitochondrial$genome$–$small$genome,$does$not$have$the$same$genes$that$bacteria$do.$$• Could$mitochondria$be$urkaryotes?$$• Excavates$have$Hydrogenosomes$–$metabolic,$take$pyruvate$and$produce$hydrogen,$acetate,$co2$and$make$atp.$Don’t$use$the$krebs$cycle.$Suggests$that$they$once$had$mitochondria,$but$lived$in$anaerobic$environments$so$they$lost$their$mitochondria.$Were$once$eukaryotes,$but$evolved$in$anaearobic$environements$and$went$under$a$selection$that$suppresses$mitochondria.$Selective$advantage$by$not$having$mitochrondia.$Excavates$were$originally$cells$with$mitochondria$but$evolved$not$to$have$them.$Stil$have$etc.$just$don’t$use$oxygen$as$the$electron$receptor$• 3$general$eukaryotic$groups$$$$2/23/11$–$Diversity$of$Unicellular$Eukaryotes$• To$get$bigger$cells,$there$needed$to$be$a$revolution$in$cell$design,$which$is$how$eukaryotes$came$about$• Eukaryotes$have$more$structural$aspects$of$diversity$• Urkaryotes$–$anaerobic$heterotrophic$cells,$nucleas$present$but$no$mitochondria$or$plastids.$• Mitchondria$arose$by$endosymbiosis.$$• Internal$organization$and$structure$of$a$chloroplast$was$very$similar$to$that$of$a$cyanobacterium.$$• The$genome$of$a$chloroplast$is$not$that$closely$related$to$the$genome$of$cyanobacteria.$Other$genes$have$been$moved$into$the$nucleus$that$increase$the$efficiency$of$the$cell.$Genes$(120$genes)$in$a$chloroplast$control$transcription$translation$and$transport.$$• All$protists$have$chlorophyll$a.$The$chlorophyll$a$is$the$reaction$center.$It$oxidizes$water$to$produce$oxygen,$H+$ions$and$electrons.$$• Protists$take$in$different$light$energys$and$different$intensities$of$photons.$• Chlorophyl$b$acts$as$antenna$molecules$to$catch$additional$light$energy$to$oxidize$water.$$• Tree$of$life$model$–$plastid$evolution,$plastid$evolved$from$photosynthetic$prokaryotic$endosymbiosis.$They$evolved$the$same$way$mitochondria$did.$Each$branch$of$lineages$hada$a$different$event$where$a$prokaryote$was$engulfed.$Primary$endosymbiosis$–$where$you$engulf$a$prok,$like$mitochondria$• Russian$doll$model$–$says$the$tree$of$life$model$is$too$simplistic,$says$some$plastids$arose$from$photosynthetic$eukaryotic$endosymbionts.$Eukaryotes$engulfed$other$eukaryotes.$Secondary$endosymbiosis$–$euk$engulfs$another$euk.$This$model$believes$some$arose$from$primary$endosymbiosis$and$some$evolved$from$secondary.$$• Glaucophytes$–$have$peptoglycan$wall$which$can$be$leftover$remnants$of$the$cyanobacteria$cell$wall.$$• Cryptomonas$–$has$4$membranes$around$nucleus,$has$a$persistant$nucleomorph$(something$that$looks$like$a$remnant$of$a$nucleus$with$linear$euk$genes),$one$set$of$70s$ribosomes$(found$in$proks)$and$2$sets$of$80s$ribosomes$(found$in$euks).$How$would$u$explain$this?$–$secondary$endosymbiosis.$A$series$of$primary$then$secondary$engulfs.$The$nucleus$of$the$algae$cell$turns$into$the$nucleomorph$in$the$end$cell.$$•
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