(A) An illustration of a hypothetical set of biochemical reactions, representing metabolic sources and sinks of phosphates. The top reaction shows that during the synthesis of a phosphate source (highlighted in green box), phosphate is released, while the bottom reaction shows that during the synthesis of a phosphate sink (highlighted in the red box), phosphate is utilized. (B) A schematic showing possible outcomes that restore phosphate during transient fluctuations in phosphate availability. Through largely mass action based processes, limitations in phosphate will promote metabolic reactions leading to the synthesis of a phosphate source metabolite, accompanied with the release of Pi. As a result of this, two possible cellular scenarios can occur- first, if phosphate levels are restored through this process, this can result in the subsequent utilization of the metabolic phosphate source and phosphate for the synthesis of metabolic sink. Alternately, if source producing reactions are insufficient to restore phosphate, this can result in continuing synthesis of metabolic sources, and the possible utilization of metabolic sinks, both of which results in phosphate release. (C) A set of key metabolic pathways, derived from glucose metabolism, illustrating the flow of phosphates, and highlighting major reactions that result in the synthesis of metabolic phosphate sources (green boxes) accompanied by Pi release, and few reactions that result in the synthesis of metabolic phosphate sinks (red boxes) accompanied by utilization of Pi.