The final protein that forms a blood clot is
...under normal conditions. Blood-clotting proteins circulate in the blood plasma in an inactive form, poised to participate in blood coagulation upon tissue injury. Blood-clotting proteins generate thrombin, an enzyme that converts fibrinogen to fibrin, and a reaction that leads to the formation of a fibrin clot. Blood-clotting proteins circulate in the blood plasma in an inactive form, poised to participate in blood coagulation upon tissue injury. Blood-clotting proteins generate thrombin, an enzyme that converts fibrinogen to fibrin, and a reaction that leads to the formation of a fibrin clot. Blood clots are clumps that occur when blood hardens from a liquid to a solid. 1  A blood clot that forms inside one of your veins or arteries is called a thrombus. 2  A thrombus may also form in your heart. 3  A thrombus that breaks loose and travels from one location in the body to another is called an embolus. When tissue damage results in bleeding, fibrinogen is converted at the wound into fibrin by the action of thrombin, a clotting enzyme. Fibrin molecules then combine to form long fibrin threads that entangle platelets, building up a spongy mass that gradually hardens and contracts to form the blood clot.... A blood protein essential to blood clotting. The conversion of fibrinogen to its active form (fibrin) is among the final steps in clot formation, and is triggered by thrombin. Fibrin is developed in the blood from a soluble protein, fibrinogen. When platelets come into contact with damaged tissue thrombin is formed as a result of a series of chemical processes (coagulation cascade) that culminate in the formation of fibrin from fibrinogen. At each stage, more clotting factors are activated. The final stage is conversion of the protein fibrinogen, which is dissolved in the fluid part of the blood, to insoluble fibrin strands. The sticky fibrin threads form a tangled mesh that traps red cells and other blood cells, forming a clot. There are 13 blood clotting proteins (coagulation factor) found in the blood. They are designated by Roman Numerals I through XIII. When a blood vessel is damaged, these clotting factors are switched on in a certain order (Blood Clotting Cascade) [link to coagulation page] and work to form a clot. In hemostasis a damaged blood vessel wall is plugged by a platelet and a fibrin-containing clot to stop the bleeding, so that the damage can be repaired. Coagulation involves a cellular (platelet) and protein (coagulation factor) component. Thrombin, in turn, catalyzes the conversion of fibrinogen (factor I)—a soluble plasma protein—into long, sticky threads of insoluble fibrin (factor Ia). The fibrin threads form a mesh that traps platelets, blood cells, and plasma.
Thrombin