MICRB 265 (10/02/13) BIOENERGETICS Part II - Fermentation and Respiration (con't) | Part III - Metabolic Diversity

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Microbiology (Biological Sciences)
Brian Lanoil

MICRB 265 (October 2, 2013) BIOENERGETICS: Part II: Fermentation and Respiration (con’t) | Part III: Metabolic Diversity Branched Electron Acceptors  Alternative terminal electron acceptors (other than oxygen) o Called reductases  Facultative aerobes prefer oxygen as electron terminal acceptors BUT it is when O 2 levels get low, reductase genes get turned on so that it can use an alternative terminal electron acceptor (ex. NO3) o Less protons are pumped out in this way though Significance of Proton Motor Force  Electrochemical gradient formed during electron transport o As electron are passed on to the next carrier, more and more protons are pumped outside of the membrane  Against their concentration gradient  The plasma membrane is impermeable to protons  First discovered in mitochondria before its discovery in bacteria o Channels take advantage of this proton concentration gradient; ATPase created ATP from ADP and P from the natural in-flow of protons from the outside of the cell to the inside Linkage of Catabolic to Anabolic Reactions Anabolism – is the production of complex molecules from simpler ones (takes energy)  Anabolism cycles with catabolism o Catabolism creates energy for fuel and for anabolism o This is important when there are limited resources and the rate of biosynthesis is balanced with that of catabolism Anapleurotic enzymes – enzymes that can take part in both catabolism and anabolism (very efficient!)  Different cofactors are used in both cases: o NADH  catabolism o NADPH  anabolism Anapleurotic reactions: TCA cycle  ½ of all our amino acids come from the TCA cycle  This cycle produces a lot of intermediates that just get converted into other intermediates for energy production BUT these intermediates can be separated from the TCA cycle to be converted into different biosysnthesis products o α-Ketoglutarate (intermediate of TCA cycle)  glutamate  proline + glutamate + arginine o Oxaloacetate (another intermediate)  aspartate  asparagine + lysine + methionine + threonine + isoleucine o Pyruvate  Alanine  valine + leucine o 3 – phosphoglycerate  serine  glycine + cysteine o Phosphoenol Pyruvate or Erythrose-4-P   chorismate aromatic phenylalanine + tyrosine +
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