In the blood coagulation cascade, vitamin K is required to introduce γ-carboxylation of clotting factors II, VII, IX, X and protein Z.

[4] In addition, upon mechanical injury to the blood vessel wall, a cell-associated tissue factor becomes exposed and initiates a series of enzymatic reactions localized on a membrane surface generally provided by cells and accumulating platelets.

Gla residues partly govern the activation and binding of circulating blood-clotting enzymes and zymogens to this exposed cell membrane surface.

Lack of these gla residues results in impaired coagulation or even anticoagulation, which may lead to bleeding diathesis or thrombosis.

Thus, citrate addition to blood is the most common method of storing it in a liquid state between harvest and transfusion.