This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood: Hemostasis and Blood Coagulation, Subject name: Physiology
Which is Vitamin K dependent clotting factor? 
Select and explain. 
A. Factor VII, B. Factor I, C. Factor XI, D. Factor XII
A: Factor VII
Answer: A: Factor VII 
Explanation: Ans is 'a' i.e. Factor VII Vitamin K serves as an essential cofactor for an enzyme carboxylase that catalyzes carboxylation of glutamic acid residues on vitamin K-dependent proteins. The key vitamin K-dependent proteins include:Coagulation proteins: factors II (prothrombin), VII, IX and XAnticoagulation proteins: proteins C, S and ZOthers: bone proteins osteocalcin and matrix-Gla protein, and certain ribosomal proteinsThese proteins have in common the requirement to be post-translationally modified by carboxylation of glutamic acid residues (forming gamma-carboxyglutamic acid) in order to become biologically active.