Question

Blood protein which initiates blood coagulation is
A) Prothrombin
B) Thrombin
C) Fibrinogen
D) Fibrin

Answer 1

Coagulation is also known as blood clotting. In this process the blood changes from liquid to gel. The thickening of blood is caused due to an injury. It results in the stoppage of the blood loss from the site of injury.

Complete answer:
To answer this question, we must know about the process of blood clotting. Blood clotting takes place at the site of injury. It results in the thickening of the blood which causes cessation of the blood loss from the site of injury.

Platelets present in the blood are responsible for the process of clotting. The mechanism of clotting is initiated by the prothrombin. The various steps involved in blood clotting are-

The clotting factors convert the blood protein prothrombin to activate thrombin.
The thrombin further converts the fibrinogen into fibrin.
This fibrin forms a network and traps RBC and platelets at the site of injury and forms a clot.

-Thrombin- It is the principal enzyme for blood clotting. It converts the fibrinogen to fibrin.
-Fibrinogen- It is a glycoprotein made by the liver. It circulates in the blood of all vertebrates.
-Fibrin- It is a mesh like network which forms at the site of injury and thus stops bleeding.

Hence, the correct answer is option ‘A’.

Note: The clotting requires coagulation factors, calcium and phospholipids. Prothrombin is a plasma protein essential for blood clotting. Prothrombin is a protein manufactured by the liver. There are 13 essential coagulation factors required for the process of clotting.