Final answer:
Activated proteins in the coagulation cascade, before the final formation of fibrin, are D. enzymes. These enzymes act in a series to lead to a fibrin clot, key in the stabilization of forming blood clots.
Step-by-step explanation:
Each step in the coagulation cascade involves the activation of one protein by another. These proteins are generally inactive precursors that become activated to trigger the next step in the cascade, leading up to the formation of a blood clot. The types of molecules that these activated proteins are, other than the final fibrin product, is D. Enzyme.
Fibrinolysis is the process where the stabilized clot is acted upon by contractile proteins within the platelets, which tighten the fibrin threads and squeeze out serum. This action can be likened to tightening loose shoelaces. In the common pathway of coagulation, once factor X is activated, it leads to the conversion of prothrombin (factor II) into thrombin, which then transforms fibrinogen (factor I) into fibrin, and is finally stabilized by factor XIII.