Microbes transfer energy by moving electronsReduced food molecules --> Energy Carriers --> Membrane protein carriers --> Oxidized minerals"Proton motive force"- Drives protons across the membrane (stores energy to make ATP)Electron Transport Systems (ETS)Reduced electron donor to oxidized electron acceptorTransfer of e- through series of membrane-soluble carriers called ETSEnergy-acquiring processes using ETS1. RespirationOrganic e- donors and inorganic/organic terminal e- acceptors 2. LithotrophyInorganic e- donors and inorganic/organic terminal e- acceptors 3. PhototrophyLight capture by cholorophyll, coupled to splitting of H2S or H2O or organic moleculesOxidoreductases- electron transport proteinsOxidize one substrate (remove e-) and reduce another (donate e-)Consist of multiple-protein complexes including cytochromescytochromes- colored proteins whose absorbance shifts when change in redox state.Ex. purple bacteria (Bacteriorhodopsin-retinal)Proton Motive ForceTransfer of H+ through proton ump generates electrochemical gradient of protonsdrives conversion of ADP to ATP via ATP synthaseProcess: Chemiosmotic theoryOther processes: Rotation of flagella, uptake of nutrients, efflux of toxic drugsRespiratory ETSCytochromes associate electron transfer with small energy transitions, mediated by cofactorsEnergy transitions involve the following molecular structures:Metal ions (Fe, Cu)- held in place with AA residuesConjugated double bonds and heteroaromatic rings (nicotinamide ring of NAD+/NADH)Oxiodoreductase Protein ComplexesRespiratory ETS includes 3 functional components1. Initial substrate oidoreductase (or dehydrogenase)2. Mobile electron carrier (quinone)3. Terminal oxidase ETS Pathway1. Substrate dehydrogenase receives pair of e- from organic substrate (NADH) or inorganic substrate (H2)2. Donates e- ultimately to mobile electron carrier (quinone)... Quinone to Quinol3. Oxidation of NADH and reduction of Q coupled to pumping 4H across membrane4. Terminal oxidase complex (cytochrome) receives 2 e- from Quinol5. Terminal oxidase complex transfers 3- to terminal e- acceptor, such as O2. Forms H2OE.Coli ETS pump up to 8H+ for each NADH molecule, up to 6 H+ for each FADH2 molecule.Mitochondrial RespirationMitochondria only have single ETSDifference between bacterial ETS1. Intermediate cytochrome oxidase complex transfers e-.2. Mitochondrial ETS pumps more protons per NADH.3. Homologous complexes have numerous extra subunits.F1FO ATP SynthaseHighly conserved protein complex, 2 partsF0 embedded in membrane, pumps protonsF1 in cytoplasm, generates ATPAnaerobic RespirationUnique to prokaryotesPossess alternative e- donors and e- acceptorsLithotrophyAcquisition of energy by oxidation of inorganic electron donorsNitrogen oxidation Ammonium to Nitric AcidSulfur and Metal Oxidation Can cause severe environmental acidification, eroding structures. Iron problem.HydrogenotrophyUse of molecular Hydrogen as electron donor.H2 sufficient reducing potential, donate e- to biological e- acceptorsIncludes chlorinated organic molecules, dehalorespiration (Potential for bioremediation)MethanogenesisReduction of CO2 and other single-carbon compounds to methaneOnly via archaea called methanogensPhototrophyHarnessing of photoexcited e- to power cell growthMore ancient form of phototrophy than chlorophyllBacteriorhodopsinSingle-protein light driven proton pumpFound in halophilic archaeaProteorhodpsin found in marine proteobacteriaSurround molecule, retinal, linked to lysine residuePhoton absorbed by retinal shifts trans to cisTrans pumps 1H+ from cytoplasm across membranedrives ATP via F1F0 ATP synthaseMax light absorption, archaea pack entire cell membrane w/ bacteriorhodopsinForms purple membraneChlorophyllsContains chromophore- light-absorbing energy carrierChlorophyll differs in substituent groups around ringSlight differences alter absorption spectraAntenna Complex and Reaction CenterMax light absorption, chlorophyll grouped in antenna complexarranged like satellite dishClusters associate ring around Reaction Center (RC)Protein complex where chlorophyll photoexcitation connects to ETCPurple bacteria, photon uptake efficiency increased by thylakoidsThylakoids- extensive back folding of photosynthetic membranes in oval pocketsPhotolytic ETSAll forms of photolysis share common design1. Antenna system2. Reaction Center Complex3. Electron Transport System4. Energy CarriersPhotosystem IGreen sulfur bacteriaSeparates e- associated w/ hydrogens from succinate, or even from reduced irone- ultimately transferred to NAD+ or NADP+.Reduced carrier (NADH or NADP) provides reductive energy for CO2 fixation and biosynthesis.Bacteria using PSI also generate net proton gradient to drive ATP synthesisPhotosystem IIPurple Nonsulfur bacteriaSeparates e- from bacteriochlorophyll itselfe- transferred to ETSan e- ultimately returned to bacteriochlorophyllCyclic photophosphorylation- this process which generates ATPPSII unlike PSI, provides no direct way to make NADH or NADPH for reductive biosynthesis Oxygenic Z PathwayCyanobacteria and chloroplastsHomologs of PSI and PSII8 photons absorbed, 2 e- removed from 2H2O, ultimately producing O2.Oxygenic Photosynthesis forms 3 ATP + 2 NADPH per 2H2O photolyzed and O2 produced.ATP and NADPH fix CO2 into