Question

Which of these are necessary for initiation of blood clotting processes?
A) Prothrombinase and thrombin
B) Tissue factor hageman factor and $Ca^{2+}$
C) Prothrombinase and $K^+$
D) Prothrombinase, tissue factors and $Ca^{2+}$

Answer 1

Hint: Blood clotting is a major mechanism seen in organisms, where normal blood converts into a gelatinous plug like structure when there is wound on the skin.

Complete answer:
Clotting of blood is seen when there is injury on the skin or sometimes internal clotting is also seen. If there is no mechanism as such to stop the blood which is oozing out of there body then that organism may turn anemic and this condition may be fatal.Blood clotting is a type of cascade mechanism which consists of activation of about thirteen tissue factors which play a role in activation of fibrinogen to create mesh work in the region of wound. Activation of tissue factors is followed by the aggregation of blood platelets. Blood clotting occurs in two major pathways Tissue factors pathway and contact pathway. TF pages are initiated by a complex of tissue factors VIIa which sacrifices TFIX. TF X is converted to activated form Xa which later activates TFII (prothrombinase) to TFIIa( where a represents activated form) the following reactions require $Ca^{2+}$ as a cofactor.

Hence, the correct answer is option D.

Note:Activation of each tissue factor is done by previously activated tissue factors. Each activated form of tissue factors acts as a serine protease and activates the future player in the cascade.