复习氨基酸.pptVIP

We can consider the metabolism of the 20 common amino acids from two points of views: The origins and fates of their nitrogen atoms The origins and fates of their carbon skeletons The Nitrogen cycle and nitrogen fixation Assimilation of ammonia Synthesis of amino acids Amino acids as metabolic precursors Protein turnover Amino acids catabolism The urea cycle converts ammonia into urea Renal glutamine metabolism produces bicarbonate (by yourself) 17.1 The Nitrogen cycle and nitrogen fixation 17.2 Assimilation of ammonia Ammonia is incorporated into glutamate and glutamine (Transamination reactions) Ammonia is incorporated into carbomoyl phosphate (later) 17.3 Synthesis of amino acids The carbon chains entry into the central pathways of carbon metabolism Glucogenic amino acids Glucogenic and ketogenic amino acids Ile\ Trp\ Tyr\ Phe Ketogenic amino acids Leu \ Lys 17.7 The urea cycle converts ammonia into urea Synthesis of carbamonyl phophate The reactions of the urea cycle Ancillary reactions of the urea cycle Figure 17.39 Urea cycle. Figure 17.39 Urea cycle. Figure 22-02 Table 22-01 * * Chapter 17 Amino Acid Metabolism Glutamate dehydrogenase(GDH) Glutamine synthetase (GS) Glutamate synthase (GOGAT) GDH/GS high NH4+ concentration Organisms in rich NH4+, not in the case, such as green plants ? GS/GOGAT low NH4+ concentration NH3 Glu Gln Glu a-ketoglutarate N2 ,NO3-,NO2- Glutamate synthase Glutamine synthetase Amino acid synthesis Transamination Glutamate release ammonia in the liver Urea cycle Figure 17.1 Nitrogen cycle. A few free-living or symbiotic microorganisms can convert N2 to ammonia. Ammonia is incorporated into biomolecules such as amino acids and proteins, which later are degraded, re-form