This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
The anticoagulant normally present in animal cell is: 
Select and explain. 
A. Vitamin K., B. Heparin., C. Hyaluronidase., D. Dicoumarol.
B: Heparin.
Answer: B: Heparin. 
Explanation: Harper – 603
Heparin is used in clinical medicine to inhibit coagulation because it binds to the specific cationic site of antithrombin III, inducing a conformational change and promoting its binding to thrombin as well as to its other substrates.