Question

Formation of prothrombinase is initiated by ___________.

• A. Prothrombin
• B. Thromboplastin
• C. Fibrinogen
• D. Heparin

Hint:

Thromboplastin is the trigger molecule that starts the clotting cascade leading to thrombin formation.

Answer 1

The Correct Option is B

Step 1: Understanding prothrombinase formation.
Prothrombinase is a complex enzyme involved in the blood clotting (coagulation) process. It catalyzes the conversion of prothrombin into thrombin.
Step 2: Role of thromboplastin.
Thromboplastin (also called tissue factor) is released from damaged tissues or platelets and initiates the cascade of reactions that lead to the formation of prothrombinase.
Step 3: Analysis of options.
(A) Prothrombin: It is a substrate, not the initiator.
(B) Thromboplastin: Correct — it initiates the formation of prothrombinase.
(C) Fibrinogen: It is converted into fibrin later in clotting.
(D) Heparin: It is an anticoagulant that prevents clotting.
Step 4: Conclusion.
The formation of prothrombinase is initiated by thromboplastin.