Clotting of blood involves which one among the following clotting proteins ?
- A.Pathogen
- B.Fibrinogen
- C.Macrophage
- D.Phagocytes
Correct answer
Explanation
The correct answer is B, Fibrinogen. Fibrinogen is a soluble plasma protein that is turned into insoluble fibrin threads, which form the mesh of a blood clot.
When a blood vessel is cut, platelets gather at the wound and release substances that start a chain of reactions. Thromboplastin, with calcium ions, converts the inactive plasma protein prothrombin into the enzyme thrombin. Thrombin then changes fibrinogen into fibrin. The fibrin threads form a net that traps red blood cells and platelets, and this net hardens into a clot that stops the bleeding. Fibrinogen and prothrombin are made in the liver, and vitamin K is needed for making several clotting factors.
A is wrong because a pathogen is a disease-causing organism such as a bacterium or virus, not a protein of the blood. C is wrong because a macrophage is a large white blood cell that engulfs germs; it is a cell, not a clotting protein. D is wrong because phagocytes are cells that eat up microbes and debris; they defend the body but do not form the clot.
Exam tip: prothrombin to thrombin, then fibrinogen to fibrin; vitamin K and calcium are needed for clotting.
Practice Questions
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