metabolism iv: vi. anaerobic respiration vii. chemolithotrophy viii. anabolism
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DESCRIPTIONMetabolism IV: VI. Anaerobic respiration VII. Chemolithotrophy VIII. Anabolism. VI. Anaerobic respiration. Reoxidation of reduced electron carriers by a process analogous to aerobic respiration, but using a terminal electron acceptor other than O 2. - PowerPoint PPT Presentation
VI. Anaerobic respirationVII. ChemolithotrophyVIII. Anabolism
Reoxidation of reduced electron carriers by a process analogous to aerobic respiration, but using a terminal electron acceptor other than O2.VI. Anaerobic respirationPMF is formed and ATP is synthesized by electron transport phosphorylation.Used by microbes capable of anaerobic respiration when O2 is not available.TB
A. Anaerobic respiration external terminal electron acceptoris not O2 eg. NO3- (nitrate), Fe3+, SO4-, CO2, CO32-, fumarate or another organic molecule
Growth substratesOxidized productsfumarateNO3-SO42-CO2succinateNO2-, N2H2SCH4
1. Nitrate reductionNO3-NO2- a form of anaerobic respiration in which NO3- is the terminal electron acceptornitrate reductase used by Escherichia coli and some other microorganisms when O2 is absent
NO3-denitrification2. Denitrification reduction of nitrate all the way to N2 through anaerobic respiration Important in agriculture and sewage treatment
3. Respiration with sulfur or sulfateSO42-H2S elemental sulfur or SO42- is the terminal electron acceptorreduction
B. Less free energy is released in anaerobic respiration than in aerobic respirationOxidized form / Reduced form Reduction potentialEo' (Volts)CO2 / glucose (C6H12O2)(- 0.43)2 H+ / H2(- 0.42)NAD+ / NADH(- 0.32)SO42- / H2S(- 0.22)pyruvate / lactate(- 0.19)O2 / H2O(+ 0.82)fumarate / succinate(+ 0.03)NO3- / NO2-(+ 0.42)
VII. ChemolithotrophyUse of inorganic compounds as the energy source (primary electron donor)
A. Examples of chemolithotrophsH2hydrogen-oxidizing bacteriaH2Ssulfide-oxidizing bacteria Fe2+iron-oxidizing bacteriaNH3ammonia-oxidizing bacteria(NH3 NO2- ) NO2-nitrite-oxidizing bacteria(NO2- NO3- )
1. Example of chemolithotrophy: aerobic sulfide (H2S) oxidation H2S + 2 O2 SO42- + 2H+
2. Examples of chemolithotrophy: ammonia oxidation and nitrite oxidation
B. Possible metabolic strategies for generating energy on early earthanaerobic chemolithotrophyfermentationanaerobic respirationanoxygenic photosynthesis
H2Cytoplasmic membraneInOutA hypothetical primitive energy- generating system on early earthprimitivehydrogenaseProton motive force (PMF)2 H+inorganic electron acceptor (not O2)
VIII. Anabolism (Biosynthesis)Energy Energy source(eg. sugar or H2) WasteEnergy
Cells are made of molecules.small molecules
A. Building cell components requires
energy (ATP) reductant (NADPH) C H O N P Sa source of carbona source of nitrogensome P and other nutrients
carbon sourceenergy sourceB. Classification of organisms according to
C. Cell carbon sugarsacetyl CoA organic acidsCell carbon:
D. Sugar / polysaccharide metabolismSugars are needed forpolysaccharides (cell wall, glycogen)nucleic acids (DNA, RNA)hexosespentosessmall molecules (ATP, NAD(P)+ cAMP, coenzymes, etc.)
1. UDP-glucose is a precursor to polysaccharides and peptidoglycan.
2. GluconeogenesisA pathway for making glucose-6-P from noncarbohydrate sources (e.g. acids from TCA).
3. Gluconeogenesis is the reversal of glycolysis starting with PEP, but with a few different enzymes. TCAOAAsuccinategluconeogenesis
4. Pentose phosphate pathwaya. makes pentoses (ribulose-5-P) from the decarboxylation of glucose-6-Pb. also makes NADPH for biosynthetic reactions
5. Deoxyribonucleotides for DNA are made from the reduction of the 2'- hydroxyl of ribonucleotides.OCH2HOHONNH2NNNOdeoxy-ATP
deoxyribo-nucleotides DNAglucoseglucose-6-Pglucose-1-PUDP-glucose(uridine diphosphoglucose)ribulose-5-PSugar summaryGluconeogenesis TCA PEP OAAglycolysisUTPpolysaccharides peptidoglycan, cell wallspentose phosphate pathwayNADPHNADP+pyruvate
E. Amino acid biosynthesis 1. Requires an acid (carbon skeleton) and an amino group O C OH H2N C H Rcarboxylic acidaminogroup
2. Some carbon skeletons are made in glycolysis and the TCA cycle5 main amino acid precursorsa. -ketoglutarate (5C)b. oxaloacetate (4C)c. pyruvate (3C)d. phosphoglycerate (3C)e. PEP (3C), (erythrose-4-P)
Carbon skeletons for amino acidsPEPCO2pyruvateTCAOAA(glucose)(acCoA)-KGphosphoglycerate
3. The amino group for glutamate can come directly from ammonia.
4. The amino group for most other amino acids comes from glutamate through transamination (amino transfer). oxaloacetate (OAA)aspartate
F. Purine and pyrimidine biosynthesis is very complex.1. The carbons and nitrogens come from amino acids, NH3, CO2, and formyl (HCOO-) groups.NNNNCC**
2. Folic acid carries the formyl groups in purine biosynthesis.3. Sulfanilamide is a "growth factor analog" that inhibits purine biosynthesis by inhibiting the production of folic acid.
D. Fatty acids1. In general, saturated fatty acids are built two carbons at a time from acetyl CoA.(8)palmitic acid
2. Unsaturated fatty acids have 1 or more cis-double bonds increase fluidity of membranes
3. Acetyl CoA and succinyl CoA and play important roles in anabolism.acetyl CoA fatty acid biosynthesissuccinyl CoA heme biosynthesis
Study objectives1. Understand anaerobic respiration and the examples presented in class. Define nitrate reduction, denitrification, sulfate reduction.2. Understand chemolithotrophy and the examples presented in class.3. Examples of integrative questions: Compare and contrast aerobic respiration, anaerobic respiration, chemolithotrophy, and fermentation. Given the description of a catabolic strategy, be prepared to identify the type of metabolism being used. Contrast sulfate reduction and sulfide oxidation. 4. Be able to classify microorganisms based on energy source and carbon source.5. Understand the roles of glycolysis and the TCA cycle in the synthesis of cellular macromolecules.6. What type of polymers are synthesized from UDP-glucose?7. What are the functions of gluconeogenesis and the pentose phosphate pathway?8. How are deoxyribonucleotides for DNA made from ribonucleotides?
10. Know the sources of carbon and nitrogen for amino acid biosynthesis. How are amino groups transferred to acids to make amino acids?11. Understand the role of folic acid in nucleotide biosynthesis.12. How does sulfanilamide inhibit the growth of microorganisms? 13. Humans do not make their own folates. Why is the drug sulfanilamide toxic to certain microorganisms but not to humans? 14. Know the anabolic roles of acetyl CoA and succinyl CoA as described in class.