Prothrombin can only be converted to thrombin by the action of factor X, factor V, platelet factor 3, and:

Question

Quizplus · Accepted Answer

Calcium is required for the conversion of prothrombin to thrombin. The complex of factor Xa, factor Va, and calcium ions is known as prothrombinase, which catalyzes the conversion of prothrombin to thrombin. Without the presence of calcium, this reaction cannot occur. Factors II and fibrinogen are substrates for thrombin, but they do not play a direct role in the conversion of prothrombin to thrombin. Phosphorus is not directly involved in the clotting cascade.

Prothrombin Can Only Be Converted to Thrombin by the Action