The Cell: Basic Unit of LifeEarly earth and the origin of lifeUniversal Cell ComponentsBacteriaThe Smallest, Simplest CellsProkaryotic FeaturesBacterial Cell FeaturesAdvanced Prokaryote FeaturesBacteria are ImportantCommercial Bacteria3 Domains of LifeCampbell Fig. 27.1, 27.11, Table 27.2Phylogeny of DomainsArchaeaEukaryotesEvolution of Eukaryotic CellsCampbell Fig. 28.2OrganellesMitochondrionCampbell Fig. 7.17The Cell: Basic Unit of LifeProkaryotes and the Evolution of EukaryotesStephen J. SalekEarly earth and the origin of life• Universe is 10-20 billion years old• Atmosphere H first then other gases• Earth solidifies 4.1 bya•1st photosynthetic prokaryotes 3.5 byaUniversal Cell Components• cell membrane• cytoplasm• genetic material (DNA)• ribosomes– for protein synthesisCampbell Fig. 7.4BacteriaThe Smallest, Simplest CellsALL BACTERIA ARE PROKARYOTES.rod-shapedsphericalCampbell Fig. 27.2spirilliformProkaryotic Features• DNA is in a single-stranded loop – No chromosomes, mitosis, or meiosis– Lack a membrane-bound nucleus• No mitochondria, chloroplasts, or other organelles• Cell walls are chemically unlike any eukaryote cell wallsBacterial Cell FeaturesCampbell Fig. 7.4Advanced Prokaryote FeaturesCampbell Fig. 27.5• interior membranes• bacterial flagellum• some are photo-autotrophicCampbell Fig. 27.6compare Campbell Fig. 27.9Bacteria are Important• Pathogens (“disease-causing”) are parasites on living cells and organisms•Decomposersrot dead material, recycling essential nutrients• Mutualists with -– plants: root-knot rhizobia fix nitrogen– fungi: cyanobacteria are part of lichens– animals: intestinal bacteria digest celluloseCommercial Bacteria• Lactose-users make yogurt and cheese• Soil bacteria make many antibiotics• Intestinal bacteria used as “lab rats” in cell biology• Cyanobacteria are important for marine and freshwater food chains3 Domains of LifeCampbell Fig. 27.1, 27.11, Table 27.2• Archaea are also prokaryotes• Recently separated from Bacteria– Cell wall chemistries are different – Archaea genes more like eukaryotes’ •Only Eukarya have a proper nucleusPhylogeny of DomainsprokaryotesBacteria Archaea EukaryaArchaea• unusual environmental tolerances: – extreme halophiles– extreme thermophiles– methanogensCampbell Fig. 27.10Eukaryotes• true cell nucleus:–nuclear membrane– linear DNA, organized into chromosomes– replicate by mitosis and meiosis• Plants, animals, and fungi are eukaryotes.• Many unicellular algae and protozoans are also eukaryotes.Evolution of Eukaryotic CellsCampbell Fig. 28.2Step 1: Nuclear and endo-plasmic membranes (kingdom Archezoa)Step 2: Organelles acquired by symbiosis (remaining 7 kingdoms)Organelles• Bacteria that were parasites, became mutualists– mitochondria burn sugars, etc., for energy– chloroplasts photosynthesize more energy– chloroplasts were lost during evolution of many living eukaryotes, such as animals and fungiChloroplastCampbell Fig. 7.18MitochondrionCampbell Fig. 7.17External and internal membranes(compare to early stages of eukaryote cell