Lecture_4_ESM219_07 - If you're a microbe what do you need...

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1 ESM 219 Lecture 4: Energetics If you’re a microbe, what do you need to live? • C source • energy source (electrons!) • terminal electron acceptor (TEA or e - acceptor) • “nutrients”: N, P, S, Fe, K…. and other trace minerals Let’s focus on energy: why do you need it (if you’re a microbe)? 1. Biosynthesis : making new cells and macromolecules, i.e. fueling anabolism 2. Maintenance, repair, transport, polymerization : everything but biosynthesis. How do you get energy (if you’re a microbe)? • Electron donors and electron acceptors react in • oxidation-reduction reactions , catalyzed by • enzymes , operating along a biochemical • pathway , ultimately resulting in the formation of •A T P , adenosine triphosphate, an energy storage macromolecule Where are the “electron donors”? chemicals sunlight What are the electron acceptors? • The food (energy source) itself (fermentation), or • Something other than the energy source: – oxygen (O 2 ) for “aerobic” microbes – organics – metals The possibilities are almost endless! It just varies with the microbe and the environment (some are specialists and others
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2 Electron donors (Fuels) SUNLIGHT Glucose ORGANICS Ethanol Formaldehyde Methanol Hydrogen Ammonia Hydrogen sulfide Sulfur Iron Manganese Carbon monoxide BIOENERGETICS – examples in METABOLIC DIVERSITY TEAs (Oxidants) ORGANICS Carbon dioxide Sulfur Sulfate Sulfur Iron Manganese Nitrate Oxygen (Source: Kenneth Nealson / USC) Most Energy (chocolate!) Least Energy (celery!) Worst Oxidant Best Oxidant (Source: Kenneth Nealson / USC) Energetic couplings (e - donor and TEA): they’re not all created equal • “High” electron donors and “low” electron acceptors yield the most energy. • More energy means more productive microbes – Faster growing – Better at overcoming stressful situations Energy from e - sources is made into ATP • Energy is stored in ATP • ATP is used to fuel reactions in cells
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This note was uploaded on 08/06/2008 for the course ESM 219 taught by Professor Holden during the Fall '07 term at UCSB.

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Lecture_4_ESM219_07 - If you're a microbe what do you need...

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