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Which of the following substances, if introduced into the blood stream, would cause coagulation of blood at the site of its introduction -
A
Thromboplastin
B
Fibrinogen
C
Heparin
D
Prothrombin
Detailed Solution
Thromboplastin (thrombokinase) is released from injured tissues and platelets and initiates the clotting process.
In the presence of $Ca^{2+}$, thromboplastin activates the conversion of inactive prothrombin into active thrombin.
Thrombin converts the soluble plasma protein fibrinogen into insoluble fibrin threads, which form a network that traps blood cells and forms the clot.
So if thromboplastin is introduced into the blood stream, it will start this sequence and cause coagulation at the site of its introduction.
Fibrinogen and prothrombin are already present in normal blood in the inactive state, so adding them does not start clotting.
Heparin is an anticoagulant that prevents clotting.
So the substance is thromboplastin.
In the presence of $Ca^{2+}$, thromboplastin activates the conversion of inactive prothrombin into active thrombin.
Thrombin converts the soluble plasma protein fibrinogen into insoluble fibrin threads, which form a network that traps blood cells and forms the clot.
So if thromboplastin is introduced into the blood stream, it will start this sequence and cause coagulation at the site of its introduction.
Fibrinogen and prothrombin are already present in normal blood in the inactive state, so adding them does not start clotting.
Heparin is an anticoagulant that prevents clotting.
So the substance is thromboplastin.