P10-Lecture 18- Prokaryotes - March 24

P10-Lecture 18- Prokaryotes - March 24 - Exam results s...

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Unformatted text preview: Exam results s Mean: s S.D.: s High: 101 s Rough grade breakdown for this exam x Mean grade is a mid to high C x > Mean + 1 S.D (i.e. > 84) = A x < Mean - 1 S.D. (i.e. < 55) = D x Remember, you can drop an exam s Exam key will be posted this evening "Prokaryotes" Organisms that run the world s Dominant Life forms on Earth x 10x the biomass of Eukaryotes x Extreme metabolic diversity x The basis for eukaryotic metabolism "Prokaryotes" vs. Eukaryotes (Briefly) s Unlike Eukaryotes, prokaryotes have x No nuclear envelope x No membrane bound organelles x Circular DNA, with relatively few genes Figs. 7.1; 7.6 s Unlike most Eukaryotes, Swapping Genes Lateral (= Horizontal) Gene Transfer "prokaryotes" can laterally transfer genes!!! x Very important for evolution s Various mechanisms x E.g. transformation, transduction, conjugation. Know general Energy and Carbon s Two Basic requirements x Energy x Carbon for synthesis of organic compounds x Needn't come from the same source s Energy x Phototrophs use light x Chemotrophs use organic compounds x Lithotrophs use inorganic compounds s Carbon x Autotrophs use CO x 2 Some Basic Metabolism: Energy Transformations to make ATP s Glycolysis / Fermentation x Glucose (high potential energy) broken down x Energy used to produce ATP x Very widespread! Ancient! x Not particularly efficient x Anaerobic s Aerobic Respiration s Photosynthesis 9.17 Some Basic Metabolism: Energy Transformations to make ATP s Glycolysis s Aerobic Respiration x Continues breakdown started in glycolysis x Much higher yield of ATP! x Electrons passed down electron transport chain to an electron acceptor 3 Usually O2 (exceptions called anaerobic resp). 3 Energy harnessed to produce ATP s Photosynthesis Some Basic Metabolism: Energy Transformations to make ATP s Glycolysis s Aerobic Respiration x Fig. 28.15 x See also 9.22 s Photosynthesis Some Basic Metabolism: Energy Transformations to make ATP s Glycolysis s Aerobic Respiration s Photosynthesis x Light energy transmitted to electron x Electron passed down electron transport chain 3 Energy harnessed to produce ATP 3 Electrons come from splitting water, resulting in release of O2 (usually) Some Basic Metabolism: Energy Transformations to make ATP s Glycolysis s Aerobic Respiration s Photosynthesis x Fig. 10.16 x Also, add P. 210 column one to reading Energy and Carbon s Energy - Three ways x Phototrophs 3 Energy s Carbon - Two ways x Autotrophs 3 Carbon from light 3 E.g. plants, some prokaryotes (e.g. cyanobacteria) x Chemotrophs 3 Energy from CO2 3 E.g. plants, some prokaryotes (e.g. cyanobacteria) x Heterotrophs 3 Carbon from energy rich organic compounds 3 E.g. Animals, Fungi, some prokaryotes x Lithotrophs 3 Inorganics, from organic compounds 3 E.g. Animals, Fungi, some prokaryotes prokaryotes Energy and Carbon - Combinations s Autotrophs: x Photoautotrophs 3 Energy from light, carbon from CO2 3 E.g. plants, some prokaryotes e.g. cyanobacteria x Chemoautotrophs 3 Energy from organics (or inorganics) , carbon from CO2. 3 E.g. Some prokaryotes; Energy and Carbon s Heterotrophs: x Photoheterotrophs 3 Energy from light; Carbon from organic sources 3 E.g. Some prokaryotes x Chemoheterotrophs 3 Energy and Carbon from organic sources. 3 E.g. some prokaryotes, us. Prokaryotic Metabolism s Very diverse x All combinations discussed, and more exist x Form basis for Eukaryotic metabolism x See Table 28.3 (note difference in some terms) s Influence on a global scale x E.g. The nitrogen cycle x E.g. Earth's geological history The very early history of life The very early history of life s Earth forms about 4.5 bya s Life appears "quickly"! s Environment very different x Volcanoes x Meteor impacts x Very little oxygen s Glycolysis a widespread and primitive pathway - Implies ...? Photosynthesis Energy from the sun! s Use light as an energy source for making ATP (Light reaction) x O2 2 as a by-product (usually) 2 s Use ATP to create sugars from CO2 s These are now photoautotrophs s The oxygen revolution: x 2.5 billion years ago x The oxygen revolution: Good news, bad news s Origin of cyanobacteria x Increased Oxygen levels (eventually) x Oxygen is very reactive - breaks bonds x Bad news for anaerobic organisms s But, allowed the evolution of aerobic respiration! Aerobic Respiration s Much greater yield of ATP s In some ways, the opposite of Photosynthesis x Photosynthesis: 3ATP (from Light rxn) + CO2 Sugar + O2 + O2 ATP + CO2 x Aerobic respiration: 3Sugar Evolution is a tinkerer s 1) Pathways for production of ATP in aerobic respiration apparently borrowed from photosynthesis s 2) Anaerobic origins of photosynthesis apparent even in modern plants x Enzymes used for fixing CO 2 are interfered with by O2 -- photorespiration Diversity of Prokaryotes - Archaea Diversity of Prokaryotes - Archaea s They can inhabit extreme environments: xMethanogens - Important decomposers 3Use H2 to reduce CO2 to methane in water 10x as salty as the ocean xHalophiles 3Thrive xThermophiles - up to 105 C xAcidophiles - in pH below 1.0! 31.0 is Battery acid "Prokaryotes" - Classification x "Prokaryotes" now considered to be _?phyletic 3 United by primitive similarities x Three domains of life 27.1 Summary s "Prokaryotes" oldest, most diverse group x All combinations of energy, carbon sources s Early Earth environment anaerobic x Only anaerobic glycolysis possible - low yield x Very widespread, apparently old s Photosynthesis -> Oxygen revolution 2.5bya x Bad for anaerobes (major extinction!) x Allowed aerobic respiration!!! s Big Idea: Evolution as tinkering s Prokaryotes 3 Archaea 3 Photo, Summary x Paraphyletic - Archaea closer to us! is monophyletic x Extremely diverse metabolism Chemo autotrophs; Photo, chemo heterotrophs x Arose in an anaerobic worldx Rise of photosynthesis allowed aerobic respiration 3 Evolution borrowed pathways from photosynthesis x Diversity of Bacteria 3 Examples x Diversity of Archaea 3 Examples ...
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This note was uploaded on 05/11/2010 for the course BIOLOGY 105 taught by Professor Richard during the Spring '10 term at George Mason.

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