Final answer:
In hemostasis, prothrombin and thromboplastin with calcium ions result in the formation of thrombin, which is crucial in converting fibrinogen to fibrin and forming a blood clot.
Step-by-step explanation:
During hemostasis, prothrombin and thromboplastin, along with calcium ions in the blood, form thrombin. The process of hemostasis begins with a vascular spasm, followed by the formation of a platelet plug, and then the series of reactions known as coagulation that ultimately results in the conversion of fibrinogen to fibrin. Both the intrinsic and extrinsic pathways of the blood coagulation process lead to the common pathway, where activation of factor X leads to the conversion of the inactive enzyme prothrombin into the active enzyme thrombin, by the enzyme prothrombinase. Thrombin then acts to convert fibrinogen into insoluble fibrin protein strands, which form a mesh that traps platelets and erythrocytes to produce a blood clot.