Question

Consider the following. Assertion (A): In blood banks, clotting of blood is prevented by adding citrates or oxalates of sodium. Reason (R): Citrates or oxalates bind to Ca$^{2+}$ ions and prevent the activation of prothrombin.

• A. Both (A) and (R) are correct, (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct, (R) is not the correct explanation of (A)
• C. (A) is correct, but (R) is not correct
• D. (A) is not correct, but (R) is correct

Hint:

Blood clotting requires calcium ions. \[ \boxed{ \text{Prothrombin} \xrightarrow[\text{Ca}^{2+}]{} \text{Thrombin} } \] Sodium citrate and sodium oxalate prevent clotting by chelating Ca$^{2+}$ ions.

Answer 1

The Correct Option is A

Step 1: Evaluate the assertion. Blood collected in blood banks is mixed with sodium citrate or sodium oxalate to prevent clotting. Hence, \[ \boxed{\text{Assertion (A) is true}.} \]

Step 2: Evaluate the reason. Calcium ions are essential for conversion of prothrombin into thrombin during blood coagulation. Citrates and oxalates bind with Ca$^{2+}$ ions, making them unavailable and thereby preventing the activation of prothrombin. Thus, \[ \boxed{\text{Reason (R) is true}.} \]

Step 3: Relate the assertion and reason. Since sodium citrate and sodium oxalate prevent clotting by removing Ca$^{2+}$ required for prothrombin activation, \[ \boxed{\text{Reason correctly explains the Assertion}.} \] Therefore, \[ \boxed{(A)} \] is the correct answer.