Read What Allows Blood to Clot
Clot formation needs clotting proteins and fibrin; anticoagulants and fibrinolytic enzymes oppose it.
Blood Clotting is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Keep the clotting machinery intact
Normal whole blood has fibrinogen and other clotting factors. Serum has already lost fibrinogen after clotting; hirudin inhibits thrombin; plasmin breaks down fibrin. A normal blood sample is therefore the one most likely to coagulate.
Follow the clotting cascade
Damaged platelets release thromboplastin. In the presence of Ca²⁺, prothrombin is converted to thrombin; thrombin then converts fibrinogen into fibrin. Follow the arrows and distinguish the inactive precursor (prothrombin) from the active enzyme (thrombin).
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- ✓Whole blood contains clotting factors.
- ✓Serum lacks fibrinogen.
- ✓Hirudin inhibits thrombin; plasmin breaks fibrin.
Serum is not simply plasma with all its clotting potential intact.
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