Fosforylaatiojännitteet

Fosforylaatiojännitteet, or phosphorylation potentials, refer to the concentration-dependent differences in the free energy of ATP hydrolysis in biological systems. ATP (adenosine triphosphate) is the primary energy currency of the cell, and its hydrolysis to ADP (adenosine diphosphate) and inorganic phosphate (Pi) releases energy. However, the actual energy released is not constant; it varies with the prevailing concentrations of ATP, ADP, and Pi within a specific cellular compartment.

The standard free energy of hydrolysis (ΔG°') is a fixed value under defined laboratory conditions. In contrast, the actual free energy of hydrolysis (ΔG) is calculated using the concentrations of reactants and products and the standard free energy. A high phosphorylation potential, meaning a high ratio of [ATP] to [ADP][Pi], results in a more negative (more exergonic) ΔG for ATP hydrolysis. Conversely, a low phosphorylation potential indicates a less negative or even positive ΔG.

These potentials are crucial for driving energetically unfavorable cellular processes, such as biosynthesis, active transport, and muscle contraction. Cells maintain high phosphorylation potentials to ensure a sufficient energy supply for these essential functions. The regulation of these potentials is a critical aspect of cellular metabolism, allowing cells to adapt to varying energy demands and environmental conditions. Changes in phosphorylation potentials can signal shifts in metabolic state and are often monitored in biochemical and physiological studies.