The Role of Urea Synthesis in the Removal of Metabolic Bicarbonate and the Regulation of Blood pH

Abstract

Publisher Summary The rates of reactions, the conformations of macromolecules, the interactions among macromolecules and between macromolecules and ligands of low molecular weight, and virtually everything that exist or occur in a living cell are affected by pH. The maintenance of intracellular pH within a reasonably narrow range should be among the most important and difficult regulatory necessities in living organisms. The problem is particularly acute in microorganisms, with their very large surface/mass ratios. In multicellular animals, the regulation of pH has been generalized and in some sense simplified by transferring it from the individual cells to systemic control systems that stabilize the pH of blood and extracellular fluid. The cells of mammals, for example, have become so dependent on this stabilization of the pH of their surroundings that an increase or decrease of 0.5 pH unit seriously threatens the life of the organism. One of the most important biological advantages of the development of a closed circulation by metazoans is that individual cells are freed from the necessity to produce the machinery needed for the stabilization of pH, osmolarity, and ionic strength against wide external fluctuations and the need to expend large amounts of ATP to effect this stabilization.