1. Secondary Metabolism and Differentiation In addition to the primary metabolic reactions, which are similar in all living beings (formation and breakdown of nucleic acids and proteins as well as of their precursors, of most carbohy drates, of some carboxylic acids, etc. ), a vast number of metab olic pathways lead to the formation of compounds peculiar to a few species or even to a single chemical race only. These reac tions, in accord with CZAPEK (1921) and PAECH (1950), are summed up under the term "secondary metabolism," and their products are called "secondary metabolites. " The wide...

Three years have elapsed since the publication of the first edition of this book (in German). The continued interest of our readers and the rapid progress of our knowl edge in many fields necessitates a thoroughly revised and somewhat enlarged new edition. Cell differentiation is a prerequisite of life. It is defined as the prooess leading to the qualitatively and quantitatively selective realization of distinct parts of a given genetic material. Cell differentiation comprises five main aspects: (1) signal reception and transformation, (2) selective rearrangements of the genetic material, (3)...