Microbiology 201 9.26 to 9.30
Microbiology 201 9.26 to 9.30 MICRB 201
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This 5 page Class Notes was uploaded by Julianna Sickafus on Sunday October 2, 2016. The Class Notes belongs to MICRB 201 at Pennsylvania State University taught by OLANREWAJU SODEINDE in Fall 2016. Since its upload, it has received 112 views. For similar materials see Introductory Microbiology in Microbiology at Pennsylvania State University.
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Date Created: 10/02/16
Microbiology 201 9/26 to 9/30 Oxidation of Glucose -complete oxidation takes place in 3 steps 1) Conversion of glucose to pyruvate -3 main pathways in microbes a) Glycolysis -main pathways for glucose breakdown -other sugars fed into this pathway -converted to glucose or derivative -2 stages involved -6 C stage -2 ATP used -3 C stage -ATP and NADH generated -ATP generated via substrate level phosphorylation b) Pentose Phosphate Pathway -more important for biosynthesis than energy production -produces main reductant NADPH -generates 3C-7C sugars -used as substrates for biosynthesis -produces ATP via conversion of glyceraldehyde-3- phosphate to pyruvate -key enzymes: -transketolase -transaldolase c) Entner-Doudoroff Pathway -used in place of glycolysis by many intestinal microbes -produces ATP, NADH, and NADPH 2) Krebs Cycle -pyruvate from glycolysis is initially converted to acetyl coenzyme A before joining cycle -acetyl coenzyme A is derived from decarboxylation of pyruvate by a pyruvate dehydrogenase complex -indirect source of large amounts of ATP -for each acetyl coA -1 FADH 2 3 NADH, 1 GTP/ATP, 2 CO 2 -provides carbon skeleton for biosynthesis 3) Oxidative Phosphorylation -ATP made via oxidation of NADH and FADH 2 -electron transport chain (ETC) accepts electrons from NADH and FADH 2 -O 2s final electron acceptor -aerobic respiration -not O 2s final electron acceptor -anaerobic respiration -energy released in process of electron transport -redox reactions -negative E 0o more positive E 0 -energy is used to pump protons out of cell against concentration gradient -forms a proton potential or proton motive force -can be used to do work -ATP synthesis -using membrane bound ATP synthase complex -process known as oxidative phosphorylation -occurs on: -plasma membrane of bacteria -cristae of mitochondria in eukaryotes -in eukaryotes: -each NADH generates 3 ATP -each FADH g2nerates 2 ATP Fermentation -generates a lot of incompletely oxidized waste products that are excreted from cell -pyruvate does not feed into Krebs cycle -NADH from glycolysis is not oxidized by ETC -low energy process -how to regenerate NAD from NADH: -if NAD is not regenerated -> death of cell -NADH oxidized by an organic molecule such as pyruvate or a derivative -in fermentation reactions, organic molecules can act as both electron donors and electron acceptors -yields a wide variety of products -alcohols, acids, aldehydes -have food and industrial applications -serve as a diagnostic tool of identification of Enteric bacteria Anaerobic Respiration -involves use of an ETC to oxidize NADH and FADH 2 -final electron acceptor is molecule other than O 2 -nitrates -> nitrites -> nitrogen (dissimilatory nitrate reduction) -sulfates -> H 2 (dissimiliatory sulfate reduction) -CO 2> methane (by methanogens) -less productive process than aerobic respiration Redox Couple E 0 NAD/NADH -0.3 NO 3NO 2 +0.4 O 2H 2 +0.8 -more productive than fermentation -no ETC Use of Macromolecules Other Than Glucose a) carbohydrates -broken down via hydrolases and phosphorylases -to monosaccharides b) lipids -lipase breaks into glycerol and fatty acids -glycerol to glycolysis -fatty acids converted acetyl coA or reduces electron carriers c) proteins -proteases broken into amino acids -deaminases amino acids -used in Krebs cycle as substrates Photosynthesis -conversion of light energy to chemical energy (ATP, NADPH) -carbon fixation -CO 2> carbohyrates -production of O 2 -2 parts to photosynthesis 1) light reactions -result in ATP, NADPH, O 2eleased 2) dark reactions (light independent reactions) -carbon fixation Light Reactions -light is harvested by the antenna -composed of proteins and pigments such as: -chlorophyll -carotenoids -in cyanobacteria and photosynthetic eukaryotes: -presence of 2 photosystems -connected via antenna -connected to ETC -ATP formed by an ATP synthase similar to the one used during respiration -photophosphorylation -cyclic: -electron transferred cyclically between photosystem I (PSI) and ETC -ATP generated -non cyclic (linear): -involves PSII, PSI, and ETC -ATP, NADPH, and O ge2erated -ETC localized on thylakoid membrane of chloroplast (eukaryotes) and specialized invaginations of plasma membrane in photosynthetic bacteria Biosynthesis/Anabolism -construction of complex macromolecules from simpler precursors -amino acids -> proteins -monosaccharide -> polysaccharide -requires energy input (ATP) and reductants (usually NADPH) -NADPH from pentose phosphate pathway -use of substrates from amphibolic pathways: -few common precursors generate a large range of end products -NADH- catabolism -NADPH- anabolism -CO 2ixation -basis for accumulation of carbohydrates on earth -occurs during light independent reactions of photosynthesis -performed by autotrophs -pathway known as Calvin Cycle or Reductive Pentose Phosphate Pathway -5 C sugar + CO = 2 3C sugar 2 -via enzyme carboxylase (rubisco) -3 stages 1) carboxylation -C fixation reactions - inorganic C to organic C 2) reduction -consumes ATP and NADPH from light reactions 3) regeneration -produces carbohydrates -regenerates RuBP -similar to oxidative pentose phosphate pathway -6 turns of the Calvin Cycle produces 1 6C sugar -fixation of 1 CO2used 3 ATP and 2 NADPH -light reactions take place on membranes -thylakoids -light independent reactions take place in soluble compartment -bacteria -> cytoplasm -eukaryotes -> stroma of chloroplasts -2 ETC is eukaryotic photosynthetic cells -1 ETC in photosynthetic bacteria -used for photosynthesis and respiration