Citric acid is a key metabolic intermediate. Citrate is the starting point of the tricarboxylic acid cycle. Its concentration also coordinates several other metabolic pathways. Citric acid can form complexes with various cations, particularly with iron and calcium. In animals, citric acid improves the utilization of nutritional calcium. Citric acid is produced commercially by fermentation of carbohydrates derived from corn starch and from beet molasses.
Citric Acid, Trisodium Salt, Dihydrate is used as a substrate for citrate lyase, a buffer component; an anticoagulant. For anticoagulation use it is typically used at a concentration of approximately 0.129 M (i.e. for 4.5 mL blood use 16.0 mg sodium citrate and 2.1 mg citric acid).