Question

Deficiency of Vitamin K makes blood clotting difficult because it is essential for
A) Change of Thromboplastin to thrombin
B) Platelet
C) Prothrombin synthesis
D) Fibrinogen Synthesis

Answer 1

Hint:Most of the Vitamin acts as a cofactor for an enzyme which is involved in biochemical synthesis. Thus deficiency of vitamin causes such enzyme to be non-functional and there will be a deficiency of the product which these enzymes form.

Complete answer:
Blood clotting is a multistep biochemical pathway involving many clotting factors. There are 12 clotting factors which include Prothrombin, Fibrinogen, Calcium etc. Most of these cofactors are synthesised in a liver with some enzymatic process. Vitamin K acts as a cofactor for the enzyme involved in prothrombin synthesis in the liver. Thus deficiency of vitamin K results in the deficient production of prothrombin and hence blood coagulation will be affected.

Vitamin K acts as a cofactor for the enzyme ‘gamma-glutamyl carboxylase’. This enzyme adds the carboxyl group during the post translational modification of prothrombin. If the Carboxyl group is not added then prothrombin will remain inactive. This carboxylation is important for binding of prothrombin to calcium during the clotting process. Deficiency of Vitamin K can arise due to less green leafy vegetables in the Diet.

Additional Information: Vitamin K is a fat soluble vitamin. There are three forms of the vitamin K
Vitamin K1 (Phylloquinone), Vitamin K2 (Menaquinone) and Vitamin K3 (Menadione) .
The daily requirement of Vitamin K is around 90-120 microgram/day. Vitamin is also synthesised by the bacteria present in our gut.

Thus the correct answer is option ‘C’- Prothrombin synthesis.

Note:Apart from dietary deficiency Vitamin K deficiency can also arise due to excessive use of certain anticoagulant such as Warfarin as they interfere with the action of vitamin K. Thus people taking a anticoagulant for a prolong time should also be supplemented with vitamin K.