Question

Mechanism of blood clotting is given below:
An injury or a trauma stimulates the platelets in the blood to release certain factors which activate the mechanism of coagulation. An enzyme complex, ______P_______ is formed by a series of linked enzymic reactions (______Q_______process) involving a number of factors present in the plasma in an inactive state. This enzyme complex is required for formation of______R_______. _____S_______ ions play a very important role in clotting.
Identify the correct option that represents P, Q, R, and S.

• A.

  P	Q	R	S
  thrombokinase	inhibitory	prothrombin	magnesium

• B.

  P	Q	R	S
  prothrombin	cascade	thrombin	magnesium

• C.

  P	Q	R	S
  thrombin	cascade	thrombokinase	calcium

• D.

  P	Q	R	S
  thrombokinase	cascade	thrombin	calcium

Answer 1

Answer: (D)

Mechanism of blood coagulation or clotting
A. Injury or trauma results in:
I. Stimulation of platelets $ \rightarrow $ Release of certain factors that activate the mechanism of coagulation.
II. Damaged tissues $ \rightarrow $ Release of certain factors that can also initiate coagulation.
B. A series of linked enzymic reactions (cascade process) that involves a number of clotting factors present in the plasma in an inactive state is initiated that finally results in the formation of an enzyme complex - Thrombokinase.
C. Prothrombin ---------- Thrombokinase-------- $ \rightarrow $ Thrombin
D. Fibrinogens in the plasma ---------- Thrombin-------- $ \rightarrow $ Fibrins
- Calcium ions are very important for clotting.