CitratKomplexformen

CitratKomplexformen refers to the various chemical forms that citrate can exist in, particularly in biological and chemical contexts. Citric acid is a weak tricarboxylic acid, meaning it can donate three protons. In aqueous solutions and biological systems, it exists in equilibrium with its conjugate bases: citrate, hydrogen citrate, and dihydrogen citrate. The specific form or "complex form" depends heavily on the pH of the environment.

At a pH below its first dissociation constant (pKa1, approximately 3.13), citric acid is largely undissociated. As the pH increases above pKa1, the first proton is lost, forming dihydrogen citrate. Above the second pKa2 (approximately 4.76), dihydrogen citrate loses another proton to form hydrogen citrate. Finally, above the third pKa3 (approximately 6.40), hydrogen citrate deprotonates to form the fully ionized citrate anion.

In biological fluids, which are generally maintained within a narrow pH range, citrate typically exists as the citrate anion or hydrogen citrate. These charged species can interact with metal ions, forming citrate complexes. For example, calcium citrate is a common form. The ability of citrate to chelate or bind metal ions is a crucial aspect of its biological function, influencing mineral absorption and metabolism. Understanding these complex forms is important in fields ranging from biochemistry and nutrition to pharmaceuticals and food science.