BIOL 112 1st Edition Lec-ture 11 Outline of Last Lecture I. Problems with Earliest DivergencesII. “LUCA”III. The Prokaryotic CellIV.Cell Wall BiochemistryV. Gram Positive/Gram NegativeVI.Ways to Organize the Cell WallVII. Structures Outside Cell MembraneVIII. Structures Inside Cell MembraneIX.Metabolism/NutritionX. AutotrophyOutline of Current LectureXI.HeterotrophyXII. Systematics/TaxonomyXIII. Three DomainsXIV. Domain ArchaeaXV. Domain BacteriaXVI. Recent Historical TrendsXVII. Distinguishing Characteristics of EukaryaXVIII. Endosymbiont TheoryXIX. Sequence of Endosymbiotic EventsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LectureI. HeterotrophyObtains energy and carbon structures from consumption of organic matter. Must “eat”something organic•Photoheterotrophs: Can photosynthesize, but still need organic carbon source for syntheses•Chemoheterotrophs: Most prokaryotes fit into this category. Differ-ent types, depending upon source of carbon food•Saprobes: Decayers, decomposers. Absorb nutrients from enzymatichydrolysis of dead organic matter•Critical components in ecological systems, recycle specific ele-ments: N, P, C, S within system•Symbionts: Some prokaryotes live in association with other organ-isms, derive carbon nutrients from living organic matter (host)•Mutualism: relationship is beneficial to both partners•Commensalism: one symbiont benefits while the host is neither harmed nor helped•Parasitism: Symbiont benefits, host is harmed Prokaryotic para-sites are also known as pathogens (disease causers)II. Systematics/TaxonomyProkaryotic and lower eukaryotic systematics are undergoing major revisions. Consequence of lots and new molecular data that is being collected. Data and new relationships are still being sorted out, so present schemes will undoubtedly be revised more in coming yearsOne consequence is development of domains, reflecting fundamental,ancient evolutionary divergences. There are three domains…III. Three Domains•Domain Archaea: Archaebac-teria. Probably represent ex-tremely ancient forms, similarto life on the planet 2-3 billionyears ago. More similarities toeukaryotes than to bacteria.Prokaryotic, adapted to livingin extremely harsh environ-ments not available to otherlife forms, but recent work in-dicates they might be widelydistributed in common envi-ronments as well•Domain Bacteria: True bac-teria. Prokaryotic cells, mostclassical bacterial forms•Domain Eukarya: EukaryotesIV. Domain Archaea•Very ancient-like forms, have a number of fundamental differences from true bacteria which distinguish them•Cell Walls — variable content•Many use proteins in cell wall•No peptidoglycan•Cell Membrane: Lipid content differs, some lipid moieties are branched.•Ribosomes and RNA polymerase more like eukaryotic forms than other prokaryotes, drug sensitivity also eukaryote-like•Archaea are more common than originally thought•Originally thought to be limited to extreme environments on Earth. Extreme hot, acid, or anaerobic, or saline conditions•But now, apparently more common•DNA sequences identified from wide range of environments onEarth, including symbiotic forms•Microscopic surveys show many organisms not otherwise iden-tified•Culture conditions for archaeans are not understood and not eas-ily defined, so ability to grow them in the lab and characterize them is very limited•Four Kingdoms:•K. Euryarchaeota•K. Crenarchaeota•K. Korarchaeota•K. Nanoarcheota•Great proliferation of knowl-edge about Archaeans in thepast 25 years. Originallythought to be rare and foundonly in unusual, extreme envi-ronmentsV. Domain Bacteria•True bacteria. Prokaryotic, butwith many features that distinguish them from archaeans (see com-parison chart on previous page)•Extremely diverse group in terms of physiology, biochemistry/nutri-tion, ecology. Some species are autotrophic, some heterotrophic. Some free-living, some symbiotic. Etc.VI.Recent Historical Trends•Abandonment of K. Protista as a valid taxon•Continued elevation of lower taxa to higher levels of Linnaean hier-archy: Phylum Protozoa —> Kingdom Protista —> Several Kingdomsof Protists•Proliferation of taxa. More and more groups with fewer species in each.•Movement away from morphological criteria to define taxa towards molecular/biochemical/dynamic criteriaVII. Distinguishing Characteristics of Eukarya•Eukaryotic Cell Organization•Single-celled or colonial. No more than 1 tissue type in cell mass.•Most species are single-celled and microscopic — bigger than most prokaryotes•Diverse lifestyles, nutrition, motility•At least 120,000 speciesVIII. Endosymbiont Theory•Certain major organelle types in modern eukaryotic cell have separateancestral lineages, distinct from that of other cell parts•These organelles were once independent organisms, but now are in a tight mutualistic/symbiotic relationship comprising modern eukaryote•Thus, eukaryotic cell is a collection of original cell types living in rela-tion to one another•Evidence for Endosymbiosis:•Chloroplasts and mitochondria have their own distinct inheritance patterns and their own genetics•Morphology and size similar to bacteria; similar to gram negative forms•New chloroplasts and mitochondria arise only from the division/replication of existing organelles.•Complete removal of mitochondria or chloroplasts from cells with these organelles results in their permanent loss. Host cell has no way to regenerate lost organelles.•Both chloroplasts and mitochondria contain their own DNA, have their own full set of genetic expression enzymes and cofactors, andposses ribosomes more like bacterial ribosomes•DNA in these organelles is circular (in most species)IX.Sequence of Endosymbiotic Events•Ancestral eukaryotic cell could do glycolysis only — anaerobic. No pho-tosynthesis or oxidative phosphorylation•First event: elaboration of membranes to form endomembrane system - nuclear envelope, endooplasmic reticulum, golgi•At some point, urkaryote internalized an aerobic prokaryote•Over time, genes are transferred from symbiont to host genome (lat-eral gene transfer), so that mitochondrial genome now is of minimal size. Most genes needed for mitochondrion protein array come from nuclear expression.•Organelles surrounded by double membranes; inner membranes