sitrat

Sitrat, or citrate, denotes the tricarboxylate anion of citric acid and its salts. The citrate ion has the formula C6H5O7^{3−}; common salts include trisodium citrate (Na3C6H5O7) and tripotassium citrate (K3C6H5O7). In solution citrate behaves as a weak triprotic acid with three dissociation steps (pKa about 3.1, 4.8, and 6.4). They function as buffering agents and metal chelators.

In metabolism, citrate is an intermediate in the citric acid cycle. It is formed in the mitochondrion by citrate synthase from acetyl-CoA and oxaloacetate, then transported to the cytosol where it can be cleaved to generate acetyl-CoA for lipid synthesis or continue through the cycle. Citrate also inhibits phosphofructokinase-1 when present in excess, linking its levels to the regulation of glycolysis.

Citrate occurs naturally in citrus fruits and many other foods, contributing to acidity. In industry, citrate salts are common additives used for buffering and sequestration of divalent cations; they help regulate acidity and influence texture in foods. Food-grade calcium or sodium citrate is used as an acidity regulator (E331) and in baking and beverage applications.

In medicine and laboratory settings, citrate salts act as anticoagulants by binding calcium, and are used in blood collection tubes and transfusion products. Potassium citrate is used to help prevent certain kidney stones and to alkalinize urine; sodium citrate is used to treat acidosis and as a urinary alkalinizer in some contexts.

Safety and regulation: citrate salts are widely regarded as safe for many uses, though high intake can cause gastrointestinal discomfort.