Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

Fibrinogen is converted to fibrin through the action of which enzyme?

1. Catalase

2. Thrombin

3. Fibrinogenase

4. Caspase

The correct answer is: Thrombin

Fibrinogen is converted to fibrin through the action of thrombin, which is an essential enzyme in the coagulation cascade. When a blood vessel is injured, the clotting process is activated, leading to a series of enzymatic reactions that ultimately result in the formation of a stable blood clot. Thrombin plays a critical role by cleaving fibrinogen, a soluble plasma protein, into insoluble fibrin strands that weave together to form a meshwork, stabilizing the platelet plug and forming a solid clot. This conversion is vital for hemostasis, allowing the body to effectively stop bleeding and initiate repair processes following vascular injury. Other options listed involve different biological processes: catalase is involved in breaking down hydrogen peroxide, fibrinogenase refers to enzymes that convert fibrinogen to fibrin but is not commonly recognized as the primary agent in this conversion, and caspases are involved in apoptosis (programmed cell death) rather than coagulation.