Citrate functions as an effective anticoagulant due to its capacity to_____________?
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Answer: D. Chelate calcium
Explanation
Citrate molecules bind tightly to free calcium ions circulating within collected blood samples. This chelation process removes the ionized calcium required as an essential coagulation cofactor. Without available calcium, the enzymatic clotting cascade cannot proceed, preventing clot formation. Anticoagulants are substances that prevent blood coagulation during storage and laboratory testing. Calcium ions function specifically as Factor IV in the intrinsic and extrinsic clotting pathways. Chelation involves forming multiple bonds with metal ions to sequester them in solution.
Blood banks use citrate solutions to preserve collected donor blood components safely. Laboratory phlebotomists collect blood into tubes containing citrate for coagulation assays. Massive blood transfusions can sometimes induce transient hypocalcemia due to citrate binding. Buffering basic groups does not prevent coagulation factor activation in blood samples. Binding factor XII is not the mechanism by which citrate exerts its anticoagulant effect. Citrate chelates calcium directly rather than interacting with dietary vitamin K stores.
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