<prompt> Ion which is needed for conversion of Prothrombin to thrombin is?SodiumPotassiumMagnesiumCalcium  <response>: ANSWER: D CalciumREF: Guytons physiology 22nd edition page 459Conversion of Prothrombin to ThrombinFirst, prothrombin activator is formed as a result of rupture of a blood vessel or as a result of damage to special substances in the blood. Second, the Prothrombin activator, in the presence of sufficient amounts of ionic Cat causes conversion of Prothrombin to thrombin Figure 36- 2. Third, the thrombin causes polymerization of fibrinogen molecules into fibrin fibers within another 10 to 15 seconds. 