Question

Removal of calcium from freshly collected blood would

• A. cause delayed clotting
• B. prevent clotting
• C. cause immediate clotting
• D. prevent destruction of haemoglobin.

Answer 1

Answer: (B)

prevent clotting

Answer 2

Thromboplastin, a lipoprotein, helps in clot formation. Thromboplastin helps in the formation of an enzyme prothrombinase. This enzyme inactivates heparin and it also converts the inactive plasma protein prothrombin into its active form, thrombin. Both the changes require calcium ions. Thrombin converts fibrinogen molecule to insoluble fibrin. The fibrin monomers polymerize to form long, sticky fibres. The fibrin threads form a fine network over the wound and trap blood corpuscles (RBCs, WBCs, platelets) to form a crust, the clot. Thus, ifcalcium is removed from the blood, clotting process will not occur.