Final answer:
In both the intrinsic and extrinsic pathways, thrombin is derived from prothrombin.
Step-by-step explanation:
In both the intrinsic and extrinsic pathways, thrombin is derived from prothrombin. Once factor X has been activated by either pathway, the enzyme prothrombinase converts factor II, the inactive enzyme prothrombin, into the active enzyme thrombin. Thrombin then converts factor I, the soluble fibrinogen, into the insoluble fibrin protein strands.