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Ryerson University
BLG 251
Kimberley Gilbride

CHAPTER 26 QUESTIONS Page 647 1 What is biogeochemical cycling The oxidation and reduction of substances carried out by living organisms and abiotic processes that results in the cycling of elements within and between different parts of ecosystems the soil aquatic environments and atmosphere2 Describe the consortia of microorg that oxidize methane anaerobically Why are two physiologically distinct microbes required for this reaction 3 Define mineralization and immobilization and give examples Mineralizationthe conversion of organic nutrients into inorganic material during microbial growth and metabolismOrganic matter is decomposed to release simpler inorganic compoundsCO2 NH3 CH4 H2Immobilizationthe incorporation of nutrients such as nitrate and phosphate into organic matter so that they are temporarily unavailable for nutrient cyclingNutrients that are converted into biomass become temporarily tied up and are unavailable for nutrient cycling 4 What is unique about lignin and its degradation Lignin is an important structural component in mature plant materials composed of a complex amorphous polymers linked by carboncarbon and carbonether bondsStructurally heterogeneous there is no single lignin moleculeNo single degradative enzyme can attack lignin Fungi and streptomycetes degrade lignin by oxidative depolymerisation which requires oxygenA few microbes such as purple bacteriumcan degrade lignin anaerobically but at a very slow rate5 What C N and S forms will accumulate after anaerobic degradation of organic matter Compare these with the forms that accumulate after aerobic degradation Under oxicwith oxygen conditions oxidized products such as nitrate sulphate and carbon dioxide accumulateUnder anoxicwithout oxygenconditions reduced end products tend to accumulate including ammonium ion sulphide and methaneWITH OXYGENOXIDIZED PRODUCTS ACCUMULATE nitrate sulfate and carbon dioxide WITHOUT OXYGENREDUCED PRODUCTS ACCUMULATE ammonium sulfide and methane Page 648microinquiry 263What are the products of Denitrification nitrification dissimilatory nitrate reduction and assimilatory nitrate reduction Denitrificationnitrogen gas Nitrification nitrate NO3Dissimilatory nitrate reductionammoniae acceptor not incorporated into organic matter Assimilatory nitrate reductionorganic Nit is incorporated into organic matter Page 6491 why is nitrogen fixation important and under what circumstances does it occur Nitrogen fixation is the metabolic process in whichN2is reduced to ammonia carried out by cyanobacteria Rhizobium methanogens and other nitrogenfixing bacteria and archaea Although the nitrogenase enzyme is sensitive to oxygen nitrogen fixation can be carried out under both oxic and anoxic conditions2 describe the two step process that makes up nitrificationWhy do you think nitrification requires two different types of microbes Two step chemolithotrophic processNo single microbial genus can perform both steps of nitrification Ammonium oxidized to nitrite by nitrosomonas Nitrite is oxidized to nitrate by nitrobacter 3 What is the difference between assimilatory nitrate reduction and DenitrificationWhich reaction is performed by most microbes and which is a more specialized metabolic capability Assimilatory nitrate reduction is the reduction of an inorganic molecule to incorporate it into organic materialNo energy is made available during this process Denitrification is the dissimilatory reduction of nitrate which is used as a terminal electron acceptor to N2 gas And it is not incorporated into the organic material4 describe the anammox reactionWhy do you think it was so difficult for microbiologists to discover the microbes that perform this reaction Anoxic ammonium oxidation Aerobic reaction chemolithotrophs use ammonium ion as e donor and nitrite as e acceptorIt is reduced to Nitrogen GasN2This reaction is a shortcut to N2 directly from ammonium and nitrite without cycling through nitrate
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