Amino acids are closely connected metabolically, through their carbon skeletons, to the sugar metabolites we have seen in earlier chapters. Amino acid anabolism features many of the same simple metabolic intermediates that we have seen before, such as TCA-cycle intermediates. In amino acid catabolism, the reaction sequences converge on a few terminal pathways notably, glycolysis and the TCA cycle for the carbon skeletons, and the urea cycle for disposal of the amino nitrogens.