Question

In the clotting mechanism pathway, thrombin activate factors
A. VIII, X, V
B. XI, VIII, X
C. XI, IX, X
D. XI, VIII, V

Answer 1

Thrombin is the principal enzyme of haemostasis and it catalyse the conversion of fibrinogen to fibrin. When it is activated then it activates the factors.

Complete answer:
First of all, you should know what thrombin is. It is a serine protease which is encoded by the ${F_2}$ gene in humans and it is obtained by proteolytic cleavage of prothrombin in the coagulation cascade which then results in the reduction of blood loss.
Thrombin converts soluble fibrinogen to insoluble fibrin strands and apart from this, it also catalyzes many other coagulation related reactions. Once thrombin is activated then it acts to convert the factor XI to XIa, VIII to VIIIa, fibrinogen to fibrin, V to Va and XIII to XIIIa.
If we look at options now:

Option A is VIII, X, V. This option is incorrect as thrombin does not activate factor VIII, X, V but it activates factor XI to XIa, VIII to VIIIa, V to Va and XIII to XIIIa. Therefore, this option gets eliminated.
Option B is XI, VIII, X. This option is incorrect as thrombin does not activate factor XI, VIII, X but it activates factor XI to XIa, VIII to VIIIa, V to Va and XIII to XIIIa. Therefore, this option gets eliminated.
Option C is XI, IX, X. This option is incorrect as thrombin does not activate factor XI, IX, X but it activates factor XI to XIa, VIII to VIIIa, V to Va and XIII to XIIIa. Therefore, this option gets eliminated.
Option D is XI, VIII, V. This option is the correct one as thrombin activates factor XI, VIII,V and converts these factors i.e., XI to XIa, VIII to VIIIa, V to Va.

Thus, the correct answer is option D i.e., XI, VIII, V.

Note: Thrombin is a serine protease which activates and converts fibrinogen into fibrin and converts factor XI to XIa, VIII to VIIIa, V to Va and XIII to XIIIa. From all the options, XI, VIII, V factors are given in option D which makes it the correct option.