Abstract
This chapter deals with the metabolism of nitrogen-containing molecules, such as proteins and nucleic acids, that differs significantly from that of carbohydrates and lipids. Whereas the latter molecules can be stored and mobilized when needed for biosynthetic reactions or for energy generation, there is no nitrogen-storing molecule. The chapter elaborates how organisms must constantly replenish their supply of usable nitrogen to replace organic nitrogen that is lost in catabolism. It mentions the turnover of protein and nucleic acids, which is one of the most obvious aspects of cellular renovation and is a process that results in the continuous flow of nitrogen atoms through living organisms. Living organisms recycle organic nitrogen into a variety of metabolites before the element is reconverted to its inorganic form.
