Vlll CONTENTS 



21. The Cytoplasm by George H. Hogeboom and Walter C. Schneider 199 



I. Introduction 199 



II. Cytochemical Methods 202 



III. Biochemical Properties of Isolated Cell Structures 216 



22. Biosynthesis of Pentoses by Gertrude E. Glock 248 



I. Introduction 248 



II. The Hexosemonophosphate Oxidative Pathway as a Source of Pentose 

 Phosphate 248 



III. Pentose Phosphate Formation in Photosynthesis 254 



IV. Significance of the Hexosemonophosphate Oxidative Pathway 256 



V. Other Methods of Biosynthesis of Pentose Phosphates 262 



VI. Interconversion of Pentose Phosphates and Pentoses 266 



VII. Meiabolism of Pentoses 268 



VIII. Addendum 272 



23. Biosynthesis of Purines and Pyrimidines by Peter Reichard 277 



I. Biosynthesis of Purines 277 



II. Biosynthesis of Pyrimidines 295 



III. Addendum 306 



24. Biosynthesis of Nucleosides and Nucleotides by F. Schlenk 309 



I. Introduction 309 



II. Biosynthesis of Nucleosides 311 



III. Biosynthesis of Nucleotides 324 



IV. Biosynthesis bj^ Reaction of Pentose or Pentose Phosphate with Incom- 

 plete Pyrimidine and Purine Systems 331 



V. Role of B-Vitamins in Nucleoside and Nucleotide Synthesis 334 



VI. Addendum 336 



25. Biosynthesis of Nucleic Acids by George Bosworth Brown and Paul M. 

 Roll 341 



I. Introduction 342 



II. The Nature of the Substances Which Can be Utilized as Polynucleotide 

 Precursors 343 



III. Comparative Incorporations into Various Nucleic Acid Fractions. . . . 356 



IV. Factors Influencing Polynucleotide Biosynthesis 375 



V. Present Possibilities for Pathways of Assembly of Polynucleotides. . . 379 



VI. Addendum ^ 391 



26. The Metabolism of the Nucleic Acids by R. M. S. Smellie 393 



I. Introduction 394 



II. The Use of P^^ in Studies on Nucleic Acid Metabolism 394 



III. The Metabolism of the Purine and Pyrimidine Bases of PNA and DNA 402 



IV. The Ribonucleic Acids of the Subcellular Fractions 408 



V. Factors Affecting Nucleic Acid Metabolism 414 



VI. The Metabolism of Virus Nucleic Acids 419 



VII. The Catabolism of the Nucleic Acids 422 



VIII. Addendum 429 



