Biosynthesis-

• Glucogenesis
  • Synthesis of glucose from phosphoenolpyruvate
    • Phosphenolpyruvate can be synthesized from oxaloacetate
  • Pentose Phosphate Pathway
  • Amino acid biosynthesis
    • Carbon skeletons from glycolysis/citric acid cycle
    • Ammonia is incorporated by glutamine dehydrogenase
    • Ammonia group transferred by transaminase and synthase
  • Purine and Pyrimidine biosynthesis
    • PRPP( 5-Phosphoribosyl-1-Pyrophosphate)
      • Important precursor in synthesis of purines, pyrimidines, and amino acids
      • Made from ribose-5-phophate
      • Provides phosphoribose subunit for purines/pyrimidines
    • Purines
      • PRPP precursor for Inosine-5’-monophosphate (IMP)
        • IMP precursor for nucleotides adenosine and guanosine
      • IMP
        • Produces
          • GMP,GDP,GTP
          • AMP, ADP, ATP
        • Pyrimidines
          • Carbonyl Phosphate produced from glutamate, bicarbonate, and ATP
          • L-Aspartate and carbonyl phosphate join to produce N- Carbonyl- L- Aspartate
          • Dihydroorotate reacts with PRPP to form UMP
            • PRPP adds phosphoribose unit
          • Fatty acid Biosynthesis
            • Synthesize two carbons at a time by acyl carrier protein (ACP)
            • C₂ subunit originates from 3-carbon compound malonate which is attached to form malonyl-ACP
            • Unsaturated fatty acids
              • One or more double bonds in hydrophobic portion of molecule
              • Number of double bonds species/group specific
            • Branched Fatty acids
              • Synthesized using branched –chain initiating molecule
              • Odd carbon number fatty acids
            • Lipid biosynthesis
              • Fatty acids added to glycerol first
              • Simple triglycerides
                • All glycerol carbons are esterified with fatty acids
              • Complex lipids
                • One carbon atom paired with polar substance
              • In archaea lipids constructed from isoprene
                • Forms phytanyl or biphytanyl
              • Glycerol backbone of archaea contains also contains a polar group
            • Nitrogen Fixation
              • The ability to fix nitrogen frees an organism form dependence on fixed nitrogen in its environment and confers significant ecological advantage when fixed nitrogen is limiting.
              • Certain species of Baceria and Archaea can fix bacteria
                • Bacteria can be “free-living”, e.g. cyanobacteria, and dinitrogenase reductase are nitrogen fixing
              • Iron-molybdenum cofactor
                • Composed of iron and molybdenum in dinitrogenase
                • Reduction on nitrogen occurs at this site
              • Nitrogen is inhibited by O₂ because dinitrogenase reductase is irreversibly inactivated by O₂.
              • Obligate aerobes
                • Nitrogenase is protected from oxygen inactivation by a combination of the rapid removal of O₂ by respiration and the production of O₂-retarding slime layers
              • Heterocyst Cyanobacteria
                • Nitrogenase is protected from oxygen by its localization in a differentiated cell because the conditions are anoxic
              • Electron Flow
                • Elecctron donordinitrogenase reductase dinitrogenase N₂
                • 6 electrons are needed to reduce N₂ to NH₃
                  • 8 electrons are actually consumed in the process
                    • 2 electrons are lost as H₂ for each mole of N₂ reduced
                  • Reducing N₂
                    • Pyruvate donates electrons to Flavodoxin
                    • Flavodoxin reduces dinitrogenase reductase
                    • Electrons transferred to dinitrogenase one at a time. 2 ATP are consumed per electron