chapter five: microbial metabolism oxidation-reduction redox reaction: coupled reactions e- removed as part of H atom redox reactions aerobic respiration oxygenic photosynthesis nutritional classification: metabolic strategy E source to oxidize elight/chemical light energy phototroph chemical energy chemotroph carbon source org./inorganic carbon source org./inorganic photoheterotroph photoautotroph chemoheterotroph electron source organic/inorganic photoorganoheterotroph Purple nonSulfur bacteria electron source inorganic electron source org./inorganic photolithoheterotroph chemoorganoheterotroph photolithoautotroph chemolithoheterotroph chemoautotroph electron source org./inorganic chemoorganoautotroph electron acceptor org./inorganic chemolithoautotroph oxygen other inorganic oxygenic photosynthesis anoxygenic photosynthesis Cyanobacteria (plants) PSB, GSB, GNSB fermentation butanediol mixed acid lactic acid alcohol respiration e- acceptor oxygen/other aerobic respiration anaerobic respiration sulfur oxidizers iron oxidizers classifying respiration & photosynthesis complementary metabolism acquiring ATP: substrate level phosphorylation acquiring ATP: oxidative phosphorylation & chemiosmosis heterotrophy: respiration The ETC process The ETC overview Factors affecting the ETC Switching to fermentation electron path (oxidation) heterotrophy: respiration & fermentation inorganic eacceptor + C6H12O6 NAD CO2 NADH reduced e- acceptor ETC ADP + P lots of ATP 2 H+ C6H12O6 NAD+ organic pyruvate lactic acid ethanol & CO2 mixed acids butanediol ferm pyruvate NADH substrate P few ATP heterotrophy: respiration & fermentation respiration • inorganic e- acceptor • does NOT mean O2 • organic mole. CO2 fermentation • organic e- acceptor • organic organic mole. • incomplete H stripping, The Kreb’s Cycle The Kreb’s Cycle in detail lower ATP yield metabolism & media Chapter Five Learning Objectives 1. 2. 3. 4. 5. 6. 7. Discuss redox reactions in biological systems. Identify the redox partners in aerobic and anaerobic respiration and oxygenic and anoxygenic photosynthesis. Correctly identify the carbon, energy and electron source for an organism when given its nutritional classification (e.g., chemoorganoheterotroph). How is ATP generated in both substrate level and oxidative phosphorylation? Why is it so important that the electron transport chain is housed in a lipid bilayer membrane? Why is a terminal electron acceptor so important? What happens in a microorganism if the terminal electron acceptor of the ETC is not available? What molecules build up? What is done with these molecules? Discuss the major differences between respiration and fermentation. What are the four basic kinds of fermentation? autotrophy: chemosynthesis • chemo-: conversion of chemical E ATP • iron oxidation NAD+ NADH 2Fe2+ 2 H+ ETC carbon fixation 2Fe3+ ADP + P • sulfur oxidation H2S SO42- ATP heterotrophy NAD+ NADH + 2H ETC ADP + P ATP carbon fixation heterotrophy • -synthesis: carbon fixation (CO2 organic molecule) chemosynthesis: iron oxidation Thiobacillus ferrooxidans chemolithoautotrophy • energy = Fe2+ Fe3+ • electron = same • carbon = CO2 CH2O chemosynthesis: sulfur oxidation Sulfolobus acidocaldarius chemolithoautotrophy • energy = S2- (sulfide) / S2O32- (thiosulfate) SO32- (sulfite) • electron = same • carbon = CO2 CH2O autotrophy: photosynthesis • photo: light E chemical E – light-dependent (light) reactions – ATP & NAD(P)H “reducing power” chlorophyll NAD(P) NAD(P)H ETC H2S/H2O oxidized chlorophyll ADP + P • synthesis: – light-independent (dark) reactions – carbon fixation: piling e- onto CO2 carbon fixation ATP heterotrophy photosynthetic electron flow & chemiosmosis cyclic photosynthesis in the purple sulfur bacteria non-cyclic photosynthesis in the cyanobacteria Comparing Eukaryotic & Prokaryotic photosynthesis microbial CO2 fixation photosynthesis compared Eukaryotes Algae, Plants Prokaryotes Cyanobacteria Green Bacteria Purple Bacteria electron donor H2 O H2O or H2S sulfur compounds sulfur compounds O2 production oxygenic oxygenic anoxygenic anoxygenic anoxygenic environment aerobic aerobic anaerobic anaerobic anaerobic CO2 fixation Calvin-Benson Calvin-Benson Reverse Citric Acid (Reverse Kreb’s) Calvin-Benson amphibolism & ATP metabolic diversity: the non-sulfur purple bacteria • chemoheterotrophic growth – aerobic respiration – fermentation • photoautotrophic growth – anaerobic, anoxygenic photosynthesis H2 for e- & CO2 for C • photoheterotrophic growth – anaerobic, anoxygenic photosynthesis C6H6O4 (succinate) for both chapter 5 learning objectives 1. 2. 3. 4. 5. How is ATP generated in chemosynthesis, photosynthesis and respiration? How is the process different for each and how is it the same? Discuss the redox partners of sulfur and iron oxidizing bacteria. How do non-cyclic and cyclic photosynthesis differ? How does each produce ATP and NADPH/NADH? What is each used for? How is carbon fixed during chemosynthesis and photosynthesis? How is the process similar and how is it different? How do amphibolism, catabolism and anabolism relate to growth and repair in cells?