How can the blood coagulation (clotting) process be described?
Blood clotting encompasses a sequence of chemical reactions whose respective products are enzymes that catalyze the following reactions (that is why the clotting reactions are known as cascade reactions). In the plasma thromboplastinogen transforms into thromboplastin, a reaction triggered by tissue and platelet factors liberated after injury of the blood vessel. Thromboplastin then catalyzes along with calcium ions the transformation of prothrombin into thrombin.
Thrombin then catalyzes a reaction that makes fibrin from fibrinogen. Fibrin, as an insoluble substance, precipitates to produce a network that traps red blood cells and platelets forming the blood clot and having the hemorrhage.