Class Note for ECOL 182R with Professor Huxman at UA
Class Note for ECOL 182R with Professor Huxman at UA
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Date Created: 02/06/15
Posted on web 22306 at 930 am Evolution of Photoautotrophy 3001 182 2232006 3 PLANT ECOLOGY UNDERGRAD RESEARCH POSITIONS oMiX of lab and field work in labs of Dr Travis Huxman amp Dr Larry Venable 01520 hrsweek during semester 0Up to 40 hrsweek in summer Contact 6218220 or gregbgemailariz0naedu Ground rules Lecture notes will be posted the night before each lecture 182 portal link to my website Figures and tables from the text MAY NOT ALWAYS be posted online Additional gures or pictures will ALWAYS be available Several questions 25 will be posted after each lecture Within 12 days and study guides after a series of connected lectures is nished On email please put ECOL 182 in the subject I hold my office hours M 300400 W 200300 My lectures and style We ll take a While to get into the rhythm of things Ask questions if you don t then I ll start making it part of my lectures and I can be nasty and make everyone feel uncomfortable 1 am a creature of habit 1 lecture with a similar format each time If you don t interrupt me and force the format you require for learning we ll end up going along like everything is fine Big Questions What have been the important constraints and or principles that have shaped the evolution of plants Diversi cation Form and function How do organisms interact with their environment Community dynamics Ecosystem structure and function Maj or Points for Today The nature of the physical environment Evolutionary history of photoautotrophy structure and function of the photosynthetic apparatus Modern View of photosynthesis in plants with a focus on controls over process What is the ultimate constraint facing most plants Salient qualities of the environment Temperature range extremes Humidity evaporation precipitation Wind Soils Biotic in uences Radiation quality and quantity What is your favorite equation Interconversion of mass and energy Emc2 Hydrogen Helium Maintains the surface of the sun at 5800K Extremely high temperature results in radiation of energy as light into space 1360 W m392 at Earth s outer atmosphere 420 W m392 hits the Earth s surface global average Cosmic rays Gamma rays H Wavelength nm 1 X rays 5 f3 i1 Ultraviolet UV 102 Infrared IR A 105 106 Microwaves Radio waves VVVVNVWVVVV 400 Violet Blue 500 Green Yellow Oran e 600 g Red 700 W LIFE THE SCIENCE OF BIOLOGY Seventh Who cares about incoming radiation Discrete packets of Visible light called photons eg Plank 1901 7 Photons can be absorbed by receptive molecules 7 Photons have energy which can be converted to perform work which is wavelength dependent 7 Hertz 1887 Einstein 1905 What is your favorite constant My favorite constant Planck s constant h conversion of a photon to energy Ekhv EKZhCQL vaccum EX energy of a particular wavelength V frequency of oscillation l wavelength 0 speed of light How much energy is in sunlight 260 kJ mol391 Average daytime photosynthetic photon ux density 1000 umol In392 S391 100 seconds result in a mole of light compare to ATP hydrolysis yielding 40 to 50 kJ mol391 Consider the evolutionary history of photoautotrophy Initial events NOT well understood Large amount of lateral gene transfer and movement of genes between eukaryotic nucleus and organelles Glycolysis had already evolved For the process we observe in most photoautotrophic orgamsms Photosynthetic apparatus coopted from some other function development and evolution of of the respiratory chain Early energy conversion Photophosphorylation may also occur under abiotic conditions though with a small yield only in the absence of membranes but in the presence of molecules that might have existed already shortly after the formation of the earth s surface haemin imidazole Pi ADP gt Light gt ATP Evolution of Photoautotrophy Likely evolved from chemoautotrophs Fossils of photosynthetic Archean bacteria 36 billion yrs old Photosynthesis is found in both prokaryotes and eukaryotes Eukaryote distribution includes algae and embryophytes for our purposes this is the de nition of a plant note this is different than your text Prokaryotes distribution is throughout Bacteria and Archea Functional basics of photoautotrophy Light Excitzti an transfer Electmn transfer Pigment malecules Phylogenetic distribution of photosynthesis Prokaryotes 5 of 10 clades One of the most interesting proteobacteria approx 32 of all known bacteria species includes nitrifying bacteria those responsible for bioluminescence use HZS as an electron donor Photoaulotmphic ancestor of proteobacteria Phylogenetic distribution of photosynthesis Prokaryotes 5 of 10 clades A range of other clades including greensulfur bacteria gram positive bacteria recall peptidoglycan cell walls and lamentous green nonsulfur bacteria Importance of lateral gene transfer throughout these groups Cyanobacteria only clade with oxygenation abilities What are those Electron donor is typically water When did they evolve Oxygenation of the atmosphere Apparent derivation of haleobacteria chlorophyll from cyanobacteria Hadean Archean Prnlemmic Phnnemmic 10f H I I I BE 2 E 55quot 50 5 dlvergencenf H pnomeymrre c bacherlal llnaages f J II I I I II I I l Gym 14 I 3 T 2 l I ammla eukaryotee algae land plants i mammlH F I he fuaalla 1quot earliest prakaryntus I bio lcalcarbon h mmn eye nabamrlal been Figure 1 Sehematie repressMa a cf the ee of exygeu level an Earth dmmg the early hieron eflife modi ed from 1TH Maj n e39srulutioumj landmarks are indicated mews on The lower xaxie and majer geological period3 are indicated by brackets 011 the upper x axie Putative gages of early divergence of phmosy39mhetic pi39oim39otee are in icm ed by brackets above the lower x ii cine aseumes quotvii 33 Eyre and the ether 35 33 depending on L i i i date i2 accepted 13 The starting point fm exyge ic plmtneymheeie F gure 2720 Extreme Halop es Euryarchaeota LIFE THE SCIENCE OF BIaLDGV Seventh Edilian Figure 2120 Emma Halaphiles 00A Smauar Assumes me and w H Freeman is co LIFE THE SCIENCE OF BVDLDGY Seventh Edition Figure 2711 Cyanohacleria Pan 2 warm Smauer Assuming m andw H Freemana Co Biological soil crusts Universal Photosynthetic Structure Similar form in both prokaryotes and eukaryotes A simple dogma of photoautotrophic organisms energy acquisition a common physiological paradigm for a diverse set of organisms Structure antenna reaction center design chlorophyll based light harvesting pigments Chlorophylls can absorb visible light and delocalize energy across their molecular structure heterodimeric protein core of reaction center Two distinct yet related proteins Suggests origin as monomeric structure with gene duplication and neofunctionalization leading to novel function Chlorcphyll Stroma moleculgs LIFE THE SCIENCE aFBIDLOGY Savant Edition Figum 51 The Mulenular swucmm n chlumphyll mama smauerAssodales mm and W H Freeman a Cu Antenna Reaction Center Design One exception from this general design Halobacteria Euryarchaeota extreme saline environments Contain retinal protein system as a complex molecular structure Energy yield from this conversion is quite small no electron transport chain included Recall that retinal is found in the vertebrate eye Consequences Photosynthesis has evolved at least TWICE Chlorophyll based pigments Harvest light by transcis interconversion resulting in greater energy states all oxygen evolving photosynthetic groups use chl a all other bacteria use other chl bacteriochlorophylls Biosynthetic pathway Does this present an evolutionary problem Does biosynthesis recapitulate phylogeny Evolutionary solutions 5aminolevulinic acid l protochlorophyllidae l chlorophyll c chlorophyllide a chlorophyll a chlorophyll b bacteria chlorophylls Dimeric protein complex reaction center Converts that energy to a usable form Types 1 ironsulfur clusters 2 pheophytin and quinones From a variety of groups but in cyanobacteria and eukaryotes they coexist Coexist as Photosystern I 1 above and Photosystem II 2 Light harvesting structures Photosystem I uses reduces NADP to NADPH H Photosystem 11 uses light energy to oxidize water molecules producing electrons protons and 02 Both of these are standalone energy systems but combined they can maintain energy ow through a system STEROMA ow H Yr 39 39 2 l 7639 39 Plastocyanin 39 if gradien Oxidation W 1 of water LUIIMEN high Hquot W axcm 2 cm y E m u m gt m c u o c 39Fhu t oEQStsEn39n 39 Lstneme diagram MWMIM lenmlhhumm Mm E Lower ENERGY mating Stealing electrons capturing light energy producing high energy compounds Endosymbiotic origins of eukaryote photosynthesis Coexistence of multiple photosystems when both can be found in isolation in nature Similarities between cyanobacteria and chloroplasts Multiple endosyrnbiotic events not just one would expect there would be braches here Spirochaeles Chlamydiales Cyanobacteria Chloroplasts BACTERIA Mitochondria Proteobacteria ARCHAEA PLANTAE If mit or chl DNA were derived om nuclear DNA we Remaining EUKARYA STEROMA ow H Yr 39 39 2 l 7639 39 Plastocyanin 39 if gradien Oxidation W 1 of water LUIIMEN high Hquot Regulation of Photosynthesis Where does the ATP and NADPH following light harvesting The Calvin cycle Carboxylation enzymatic Reducing energy dependent Regeneratingenergy dependent Turns out there is plenty of light energy most of the time What regulates photosynthetic rate is carboxylation The Calvin Benson Cycle Ribulose 15bisphosphate carboxylase oxygenase rubisco catalyzes the xation of CO2 into a 5carbon compound ribulose 15bisphosphate RuBP An intermediate 6carbon compound forms which is unstable and breaks down to form two 3carbon molecules of 3PG see g 814 Rubisco is the most abundant protein in the world The Calvin B enson Cycle Consists of three or four processes LIGHT Fixation of CO2 to RuBP catalyzed by rubisco Reducing to G3P uses ATP and NADPH Regeneration RuBP uses ATP Transport by inorganic C02 phosphate Sink regulation of photosynthesis different concept of metabolic regulation in photosynthetic organisms LIGHT ADP ATP NADPH P GA PER fnoseP CYCLE m39ose PFBP F p sucP 9 suc V H RUBP hexosehP G p C02 5m Pg096 X C02 CALVIN BENSON CYCLE 6 C02 0 9 6 0 6RuBP O 6 Carbon 6 12 6 RUMP Regeneration Reduction Of RuBP and sugar production 1212 O 12 NADP 10 GBP 12 G3P 12131 2 GBP K Other carbori compounds LIFE THE SCIENCE OF mommyv Seventh Edition Figure 513 The CalvinBennquot Cycle 13 2am SmausrAssumaies inc and w H Freeman 5 Cu Making Carbohydrate from CO2 Products of photosynthesis are critical for energy on Earth Most photosynthetically acquired energy is released by glycolysis and cellular respiration of photoautotrophs Some of the carbon incorporates into amino acids lipids and nucleic acids Some of the stored energy is consumed by heterotrophs Where glycolysis and respiration release the stored energy Controls over photosynthesis Spatial heirarchy is important for understanding photosynthetic regulation Physicochernical constraints Biochemcial constraints Diffusive constraints Wholeorganism constraints 11a Thylakoids L1ght v Thylakoid a Arrangement of cells in a C3 leaf Upper epidermis quot 39Vem Spongy mesophy cell Lower epidermis CO exxernal air Sunlight LIFE THE SCIENCE OF BIOLOGY Samm Edilian Figum a The Ingre ianls for Phaiosynmasis 2004 STnanarAssacrahs Imam w H Freeman 5 c Other issues Photorespiration Rubisco is a carboxylase adding CO2 to RuBP It can also be an oxygenase adding 02 to RuBP These two reactions compete with each other When RuBP reacts with 02 it cannot react with C02 which reduces the rate of CO2 xation Photorespiration and Its Consequences Photorespiration RuBP 02 gt phosphoglycolate 3PG Glycolate diffuses into organelles called peroxisomes Peroxisornes convert glycolate to glycine Glycine diffuses into mitochondria and is converted to glycerate and C02 Figure 8 5 Organelles of Photoresplratlon LIFE THE SCIENCE OF EIOLDGV Seventh Edilion Figure 315 Organslles n1 Phntolespira on Ln 2m Smausv Assnmauas W and w H Freeman E Cu Photorespiration and Its Consequences Photorespiration uses the ATP and NADPH produced in light reactions CO2 is released rather than xed Rubisco acts as an oxygenase if C02 is very low and 02 is high 02 becomes high when stomata close preventing plant water loss Sunlight u mg mg arming mm m aw m Wm pmmmm Am a K mm m z Upper epidermis Vein Spongy mesophyll cell Lower epidermis
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