Question: The pyrimidine and purine bases are nitrogen containing compounds. What is the source of nitrogen for these two ring systems? In most examples, the reaction to add nitrogen to the growing ring structure requires an activation of a carbon atom. What is the common mechanism used to carry out this activation? Be able to recognize this when you see a reaction of this sort.
Question: The activity of ribonucleotide reductase is regulated in two ways: its total activity is controlled and its substrate specificity is controlled. What are the metabolites that regulate both of these activities? How does the cell balance the concentration of the various deoxynucleotide diphosphates? What is the principal similarity between ribonucleotide reductase and the nitrogenase complex?