**Question:** Vitamin K is involved in post-translation modification of

A. Prothrombin
B. Factor VIII
C. Factor IX
D. Factor X

**Correct Answer:** **Vitamin K is involved in post-translation modification of Factor X.**

**Core Concept:**
Vitamin K is a crucial micronutrient that plays a vital role in the synthesis of several clotting factors (coagulation factors) in the liver. The key function of Vitamin K is in the gamma-carboxylation process, which is a post-translational modification that adds gamma-carboxyglutamic acid (Gla) residues to specific amino acids in proteins. This process is essential for the proper function of these proteins.

**Why the Correct Answer is Right:**
Vitamin K is primarily involved in the gamma-carboxylation of proteins encoded by the genes clotting factors II, VII, IX, X, and XI. Among these, Factor X is the correct answer as it is the only one among options A, B, C, and D that directly relates to Vitamin K-dependent clotting factors.

**Why Each Wrong Option is Incorrect:**
A. Prothrombin (Factor II) is another Vitamin K-dependent clotting factor, but it is not the correct answer because it is not the protein directly involved in the gamma-carboxylation process.
B. Factor VIII (coagulation factor VIII) is another Vitamin K-dependent clotting factor, but it is not the correct answer as it is not the protein directly linked to Vitamin K-dependent gamma-carboxylation.
C. Factor IX (coagulation factor IX) is a Vitamin K-dependent clotting factor, but it is not the correct answer because it is not the protein directly involved in the gamma-carboxylation process.
D. Factor X (coagulation factor X) is a Vitamin K-dependent clotting factor and is directly involved in the gamma-carboxylation process, making it the correct answer.

**Clinical Pearls:**
1. Vitamin K deficiency can lead to bleeding disorders due to impaired clotting factor synthesis and function.
2. The gamma-carboxylation process ensures proper functioning of Vitamin K-dependent clotting factors, which are essential for blood coagulation and the maintenance of hemostasis.
3. The role of Vitamin K in coagulation highlights the interdependence of various clotting factors, emphasizing the importance of a balanced physiological environment for proper coagulation cascade function.