Body Fluids and Circulation Question 44
44. Removal of calcium from freshly collected blood would
(a) cause delayed clotting
(b) prevent clotting
(c) cause immediate clotting
(d) prevent destruction of haemoglobin
Show Answer
Answer : b
Hints & Solutions
(b) Removal of calcium from freshly collected blood would prevent clotting because the process of blood clotting starts when prothrombinase (an enzyme formed by thromboplastin) catalyses the conversion of prothrombin (an inactive protein in the blood plasma) into thrombin (active protein) and this reaction takes place in the presence of $Ca^{2+}$. Now this thrombin converts fibrinogen into fibrin which makes fibrin threads on polymerisation & with blood corpuscles, it clots blood. So if $Ca^{2+}$ are removed from blood it’ll prevent clotting. It may also be done by adding some anti coagulants, eg. sodium & potassium oxalates in blood as they precipitate $Ca^{2+}$ present in the blood.
