5.6 Which of the following electron donor/electron acceptor pairs represent potential energy reactions for bacterial growth? Assume that all reactants and products are at unit activity, except that pH = 7.0. Stoichiometry and Energetics Case Electron Donor Electron Acceptor a Acetate Carbon dioxide (methanogenesis) b Acetate Fe3+ (reduction to Fe2+) Acetate H+ (reduction to H,) d Glucose H+ (reduction to H,) H, Carbon dioxide (methanogenesis) Nitrate (denitrification to N,) H2 S° (oxidized to sulfate) g NO, (denitrification to N,) 3 h CH, NO, (denitrification to N,) i NH (oxidation to NO,) so?- (reduction to H,S + HS-)
Enzyme kinetics
In biochemistry, enzymes are proteins that act as biological catalysts. Catalysis is the addition of a catalyst to a chemical reaction to speed up the pace of the reaction. Catalysis can be categorized as either homogeneous or heterogeneous, depending on whether the catalysts are distributed in the same phase as that of the reactants. Enzymes are an essential part of the cell because, without them, many organic processes would slow down and thus will affect the processes that are important for cell survival and sustenance.
Regulation of Enzymes
A substance that acts as a catalyst to regulate the reaction rate in the living organism's metabolic pathways without itself getting altered is an enzyme. Most of the biological reactions and metabolic pathways in the living systems are carried out by enzymes. They are specific for their works and work in particular conditions. It maintains the best possible rate of reaction in the most stable state. The enzymes have distinct properties as they can proceed with the reaction in any direction, their particular binding sites, pH specificity, temperature specificity required in very few amounts.
Bacteria can enter the body if a puncture wound occurs. This is a deep wound caused by something sharp and pointed, such as a nail. There is not much oxygen available inside the wound so the bacteria respire anaerobically to get the energy they need to survive.
In anaerobic respiration, a molecule other than oxygen is used as the terminal electron acceptor in the electron transport chain.
Some iron reducing bacteria are able to generate energy from the reduction of FeIII to FeII while using acetate as an electron donor, namely Shewanellae and Geobacteraceae.
Inorganic compounds include sulfate (SO42-) nitrate( NO3-), and ferric iron (Fe3+), have a lower reduction potential than oxygen. Therefore, less energy is formed per molecule of glucose.
Many bacteria used electron acceptor other than oxygen.Denitrification is the utilization of nitrate (NO3-) as the terminal electron acceptor.Many denitrifying bacteria can also use ferric iron (Fe3+) and different organic electron acceptors.Ferric iron (Fe3+) is a widespread anaerobic terminal electron acceptor used by both autotrophic and heterotrophic organisms.
Sulfate reduction uses sulfate (SO42-)as the electron acceptor, producing hydrogen sulfide (H2S) as a metabolic end product. This method is used by many Gram negative bacteria found within the δ-Proteobacteria. It is also used in Gram-positive organisms related to Desulfotomaculum or the archaeon Archaeoglobus.
Acetogenesis is a type of microbial metabolism that uses hydrogen (H2) as an electron donor and carbon dioxide (CO2)as an electron acceptor to produce acetate, the same electron donors and acceptors used in methanogenesis.
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