Unity and Diversity in Biochemistry: An Introduction to Chemical Biology

By Marcel Florkin; T. Wood | Go to book overview
of a compound. In this way one can measure the turnover of a substance, that is the rate at which its molecules are replaced (although the concentration remains the same) when it is in a steady state resulting from an equilibrium between the rate of synthesis on the one hand, and the rate of breakdown or incorporation, on the other.
III. THE USE OF MUTANT STRAINS OF MICRO-ORGANISMS
The name auxotrophes is given to those mutant forms of a microorganism which are dependent on the provision of a growth factor not required by the natural form. At the present time, a very large number of mutants are known which are characterized by the loss of a given enzyme, their metabolism is blocked at the stage of a definite chemical reaction. To define the particular reaction which is blocked, two sets of information are required: a knowledge of the substances which the mutant can use as growth factors, and knowledge of the substances which accumulate in the cell. Let us suppose that A and B are two different precursors of X. If we have a mutant which is an auxotrophe for X, which accumulates A, and which responds by growing when B is supplied, we can deduce that the block is situated after A and before B in the series of metabolic reactions.
DISTINCTION BETWEEN A POSSIBLE PRECURSOR AND AN OBLIGATORY INTERMEDIATE
To show that a given substance can serve as a precursor of a second substance is one thing; to show that it is in fact the normal intermediate in the organism is quite another. The study of mutants of micro-organisms has revealed the existence of auxotrophes for each of the naturally occurring amino acids. This illustrates very well the idea of an obligatory metabolic pathway, at least in these organisms.Let us once more consider the case of A and B, precursors of X in a micro-organism. The wild strain of this micro-organism is able, as can be demonstrated by the use of isotopes or by means of the purified enzymes, to convert A and B into X. A single enzyme, extracted from the microorganism and purified, converts A into B. A mutant auxotrophic for X does
REFERENCES
CALVIN M., HEIDELBERGER Ch., REID J. C., TOLBERT B. M., YANKNICH P. F. ( 1949). Isotopic Carbon. Techniques in its measurement and chemical manipulation. Wiley, New York.
KAMEN M. D. ( 1948). Radioactive Tracers in Biology. Academic Press, New York.

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Unity and Diversity in Biochemistry: An Introduction to Chemical Biology
Table of contents

Table of contents

  • Title Page iii
  • Contents v
  • List of Abbreviations vii
  • Translator's Preface ix
  • Introduction xi
  • Part One xv
  • Chapter I - The Biosphere 1
  • Chapter II - Constituents of the Biosphere 7
  • References 14
  • References 24
  • References 30
  • References 37
  • References 43
  • References 56
  • Chapter III - Modes of Linkage by Covalent Bonds 57
  • References 60
  • References 62
  • References 77
  • References 82
  • Chapter IV - Macromolecules 83
  • References 85
  • References 93
  • References 107
  • References 111
  • Part Two - Enzymes and Biochemical Energetics 129
  • Chapter I - General Principles of Biochemical Energetics 131
  • References 150
  • Chapter II - Enzymes 151
  • References 176
  • Part Three - Chemical Reactions in the Biosphere 177
  • Introduction 179
  • Chapter I - Destructive and Non-Destructive Methods in Modern Biochemistry 181
  • References 182
  • References 184
  • References 185
  • Chapter II - Priming Reactions 186
  • References 197
  • References 199
  • References 207
  • References 209
  • References 223
  • Chapter III - Biosyntheses 229
  • Part Four - Topobiochemistry and Cellular Regulation 271
  • Chapter I - Cellular Topochemistry 273
  • Conclusions 280
  • References 280
  • Chapter II - Cellular Regulation 282
  • References 286
  • Part Five - Biochemical Diversity 287
  • Chapter I - Some Aspects of Biochemical Diversity 289
  • References 303
  • Chapter II - The Inheritance of Biochemical Characteristics 304
  • References 316
  • Chapter III - Biochemistry and Taxonomy 317
  • References 332
  • Chapter IV - Biochemical Evolution 333
  • References 335
  • References 345
  • Part Six - The Metabolism of the Biosphere 347
  • Introduction 349
  • Chapter I - Entry into the Biosphere 351
  • References 365
  • Chapter II - Departure from the Biosphere 366
  • References 370
  • Chapter III - The Cycles 371
  • References 380
  • Index 381
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