Vitamin K is required for

Options

A. Synthesis of prothrombin
B. Change of prothrombin to thrombin
C. Reaction fo calcium with prothrombin
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Vitamin K's Role**: Vitamin K is a fat-soluble vitamin that plays a crucial role in the synthesis of certain proteins required for blood coagulation (clotting).

2. **Analyzing the Options**:
- **Option 1: Synthesis of Prothrombin**: Prothrombin is a precursor to thrombin, which is essential for blood clotting. Vitamin K is indeed necessary for the synthesis of prothrombin in the liver.
- **Option 2: Change of Prothrombin to Thrombin**: This conversion is facilitated by the enzyme thrombokinase. Vitamin K is not required for this enzymatic reaction.
- **Option 3: Reaction of Calcium with Prothrombin**: The reaction of calcium ions with prothrombin to form thrombin does not require vitamin K either. Calcium acts as a cofactor in this process.

3. **Conclusion**: Based on the analysis of the options, the only correct statement is that Vitamin K is required for the synthesis of prothrombin. Therefore, the correct answer is **Option 1**.

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