Question

Which of the following proteins is responsible for spontaneous blood clotting?
A. Factor XII
B. Factor XI
C. Factor IX
D. Factor VIII

Answer 1

Hint: Upon injury bleeding may occur for some time but then coagulation takes place in order to inhibit blood loss. Coagulation occurs due to interaction of certain proteins known as coagulation factors.

Complete answer:
For blood coagulation, factor VIII is an essential protein. It is encoded by the F8 gene and also known as an anti-haemophilic factor (AHF). When in inactive form, factor VIII circulates in the bloodstream as bound to another molecule (which is called Von Willebrand factor). If there is an injury that damages the blood vessels, factor VIII becomes active. Upon activation, it gets isolated from the Von Willebrand factor. Another coagulation factor (factor IX) interacts with the active form of protein. This interaction results in a particular chain reaction due to which blood coagulates.Clot or coagulate 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 he plasma by the enzyme thrombins thrombins are formed from inactive substance prothrombin.

So, the correct option is D. Factor VIII

Note:
In order to avoid excessive loss of blood from the body, blood coagulation is the process of creating a clot. It is also called ‘thrombus’. It is a gel-like mass produced in the blood by platelets and fibrin.