Question

According to the best and Taylor theory which of the following does not play any role in blood clotting?
A. Prothrombin
B. Fibrinogen
C. Platelets
D. Calcium ions

Answer 1

Blood clotting or coagulation is an essential process which, when a blood vessel is damaged, prevents excessive bleeding. By forming a clot over the injury, platelets (a sort of blood cell) and proteins in the plasma (the liquid component of the blood) work together to avoid bleeding.

Complete answer:
Blood coagulation mechanism: As long as it is within the blood vessels, the blood remains in a fluid state. But it turns into a jelly-like mass as it comes into contact with external atmospheric conditions. It is then said that the blood is clotted or coagulated. When a blood clot is detected under a microscope, the system in which the blood cells are entangled consists of a network-like structure. From the clot, a light-yellow fluid comes out and is called serum. To explain the mechanism of blood coagulation, different hypotheses were put forward. They are THEORY BEST AND TAYLOR, THEORY OF HOWELL's, THEORY OF FULD AND SPIRO'S, The Principle of the Best and Taylor, For blood clotting, four substances are required, according to Best and Taylor. They are prothrombin, calcium, fibrinogen, and thromboplastin. Prothrombin is formed by the liver and is also found in blood plasma in small amounts. Vitamin K helps with prothrombin synthesis in the liver.
Calcium ions are present as inorganic constituents in the plasma. Fibrinogen is a soluble protein present in the plasma that has been dissolved. Thromboplastin is released from the damaged tissue when an injury is made. In the presence of calcium ions, the released thromboplastin acts against prothrombin and converts it into active thrombin. In exchange, the thrombin works on the fibrinogen, transforming it into fibrin. To form a clot, the blood cells are entangled in the fibrin cord.
The blood in the blood vessels never coagulates. It is called thrombosis if clotting happens in the blood vessels and the clot is known as a thrombus. Blood clotting of blood vessels, however, is stopped by heparin-like antithrombin. Heparin is also produced in the liver and is present in the blood.
So, the correct answer is option C-Platelets.

Note: An enzyme called thrombokinase plays an important role in blood coagulation, based on the principle of fluid and spiro theory. Nothing but thromboplastin secreted from ruptured platelets of the blood is thrombokinase. Prothrombin is expected to be converted into thrombin by the action of calcium alone, according to Howell.