Contents. List of Contributors. Preface (E.E. Bittar and N. Bittar). Cellular ATP (D.A. Harris). Purines (C.H.V. Hoyle and G. Burnstock). The Role of Multiple Isozymes in the Regulation of Cyclic Nucleotide Synthesis and Degradation (J.K. Bentley and J.A. Beavo). The Biological Functions of Protein Phosphorylation-Desphosphorylation (T.A. Woodford, S.J. Taylor, and J.D. Corbin). The Family of Protein Tyrosine Phophatases and the Control of Cellular Signaling Responses (N.K. Tonks). Cyclic Cascades in Cellular Regulation (P. Boon Chock and E.R. Stadtman). Mechanisms of Intracellular pH Regulation (G. Goss and S. Grinstein). The Membrane Na+-K+-ATPase in Cells (T.A. Pressley). Intracellular Calcium-Binding Proteins (K.K.W. Wang). ATP-Ubiquitin-Mediated Protein Degradation (A.L. Haas). Regulation of Cellular Functions by Extracellular Calcium (E.F. Nemeth). The Basis of Intracellular Calcium Homeostasis in Eukaryotic Cells (F. Di Virgilio, D. Pietrobon, and T. Pozzan). Roles of Polyamines in cell Biology (N. Seiler). Free RAdicals in Cell Biology (P.A. Southorn and G. Powis). Index.