Question

Which pair will be most important in initiating blood clotting?

• A. $C{a}^{++}$ and prothrombin
• B. Prothrombin and thromboplastin
• C. Thrombin and fibrinogen
• D. Prothrombin and fibrinogen

Answer 1

The correct option is A $C{a}^{++}$ and prothrombin

Blood exhibits coagulation or clotting in response to an injury or trauma. This is a mechanism to prevent excessive loss of blood from the body. A clot is formed mainly of a network of threads, called fibrins, in which dead and damaged formed elements of blood are trapped. Fibrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin. Thrombin, in turn, is formed from another inactive substance present in the plasma called prothrombin. An enzyme complex, thrombokinase, is required for this activation. An injury or a trauma stimulates the platelets in the blood to release certain factors, which activate the mechanism of coagulation. Certain factors released by the tissues at the site of injury also can initiate coagulation. Calcium ions play a very important role in clotting.