Thrombokinase is associated with -

(a) Elimination of urea and other excretory products from the body

(b) Production of erythrocytes from the bone marrow

(c) Pulmonary and systemic circulation

(d) Cardiac cycle and it’s regulation

(e) Enzymatic reactions in the coagulation of blood

• Thrombokinase (also called thromboplastin) is an enzyme present in blood platelets. It plays a key role in blood clotting by converting prothrombin into its active form, thrombin.
• When a blood vessel is injured, thrombokinase is released along with other platelet factors. Together, these initiate the conversion of prothrombin (inactive) to thrombin (active).
• Thrombin then converts fibrinogen (a soluble plasma protein) into fibrin, an insoluble protein that forms fibers. These fibers create a mesh network, trapping red blood cells (RBCs) and preventing their loss at the site of injury. This forms a blood clot, which remains in place until healing occurs.
• Apart from clotting, other important physiological processes include:
  • Vasopressin (Antidiuretic hormone): Regulates water reabsorption in the kidneys, thus controlling urine volume.
  • Erythropoietin: Stimulates production of red blood cells, requiring iron, vitamin B₁₂, folate, and heme.
  • Pulmonary and systemic circulation with the cardiac cycle: Ensure efficient oxygen transport via hemoglobin throughout the body.

Therefore, the correct answer is: (e) Enzymatic reactions in the coagulation of blood.