MICRB 265 (09/30/13) BIOENERGETICS: Part 2 - Fermentation and Respiration (con't)

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Microbiology (Biological Sciences)
Brian Lanoil

MICRB 265 (September 30, 2013) Bioenergetics – Part II: Respiration and Fermentation  Net ATP yield of fermentation o 2 ATP/glucose molecule  Net ATP yield for aerobic respiration o 38 ATP/glucose molecule Important Parts of the TCA cycle (Tricarboxylic Acid Cycle aka Citric Acid Cycle)  Decarboxylated pyruvate = acetyl-CoA o Acetyl-CoA is what enters the TCA cycle  NADPH is used for biosynthesis therefore it is not sent to the ETC (electron transport chain)  FADH produces 2 ATP in the ETC  NADH produces 3 ATP in the ETC  Why does FADH produce less ATP than NADH? Because its redox potential is more positive  The intermediates produced in TCA cycle are important for biosynthesis o Biosynthesis = anabolism – substrates converted into more complex products  The TCA cycle is NOT an aerobic mechanism! o Anaerobes can use the TCA cycle too! o The TCA cycle is only exclusively aerobic in mitochondria  Note that mitochondria used to be bacteria  It is thought that eukaryotes used to only be capable of fermentation before mitochondria (organelle) existed Catabolism of Other Organic Molecules: Polysaccharides and Proteins  Polymers hydrolyzed into monomers o How?  Exoenzymes are excreted by the cell and hydrolyzes surrounding proteins  Ex. Bacillus (break down of starch in a starch agar plate)  After being exposed to iodine (starch is stained black), the clear spots show areas where the starch has been broken down o Then used for energy  The catabolism of these complex molecules is common and widespread (although not every organism is capable of it) Catabolism of Lipids  Lipids broken down 2 carbons at a time o These 2 carbons removed are in the form of acetyl-CoA which gets sent off to the TCA cycle  Key ingredients: o NAD o FAD o Coenzyme A o Dehydrogenases o Hydrases  Oxidation occurs at the β-carbon of the lipid Respiration and Phosphorylation  In aerobes: - o e given to O  2 O 2  For anaerobes: o e is given to a terminal electron acceptor other than O (e2. NO , F3 , S3 ) 42- dehydrogenases – are enzymes within bacteria that can send H dire2tly into the ETC (only a select few organisms have this enzyme)  NADH + H = universal fuel source (reductant currency) for catabolism Aerobic Electron Transport Chain -  Protons get sent outside of the cell and the e are kept and sent further down in the ETC  High concentration of H outside the c
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