Which substrate is converted to fibrin by thrombin?

Which substrate is converted to fibrin by thrombin?

• A. D-Dimer
• B. Fibrinogen
• C. Prothrombin
• D. Factor XIII

Answer: (B)

Thrombin's action target in forming a clot is fibrinogen. Thrombin cleaves fibrinogen, removing fibrinopeptides A and B to produce soluble fibrin monomers, which then polymerize to form an insoluble fibrin mesh that stabilizes the clot. After this, thrombin also activates Factor XIII to crosslink the fibrin, strengthening the clot. The other options aren’t substrates for becoming fibrin: D-Dimer is a product of breakdown of crosslinked fibrin, not a substrate that thrombin converts to fibrin; Prothrombin is the precursor that becomes thrombin; Factor XIII is the crosslinking enzyme activated by thrombin, not something converted into fibrin.

Thrombin's action target in forming a clot is fibrinogen. Thrombin cleaves fibrinogen, removing fibrinopeptides A and B to produce soluble fibrin monomers, which then polymerize to form an insoluble fibrin mesh that stabilizes the clot. After this, thrombin also activates Factor XIII to crosslink the fibrin, strengthening the clot.

The other options aren’t substrates for becoming fibrin: D-Dimer is a product of breakdown of crosslinked fibrin, not a substrate that thrombin converts to fibrin; Prothrombin is the precursor that becomes thrombin; Factor XIII is the crosslinking enzyme activated by thrombin, not something converted into fibrin.